Class 6

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 1 सूर्य तारा से भरा आकाश offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 1 Question Answer – सूर्य तारा से भरा आकाश

अति लघु उत्तरीय प्रश्नोत्तर (Very Short Answer Type) : 1 MARK

प्रश्न 1.
आकाशीय पिण्डों को किस नाम से जाना जाता है?
उत्तर :
ज्योतिष्क।

प्रश्न 2.
दिन के समय क्या आकाश में तारे देखे जा सकते हैं?
उत्तर :
नहीं।

प्रश्न 3.
एक दूसरे के समीप स्थित तारे को किस नाम से जाना जांता है?
उत्तर :
नक्षत्र मंडल।

प्रश्न 4.
आकाश में उत्तर दिशा में सात उज्ज्वल तारों को क्या कहा जाता है?
उत्तर:
सप्तर्षिमंडल।

प्रश्न 5.
सूर्य का प्रकाश पृथ्वी तक पहुँचने में कितना समय लगता है?
उत्तर :
4 मिनट 20 सेकेण्ड लगभग।

प्रश्न 6.
प्रकाश का वेग कितना होता है?
उत्तर :
1 सेकेण्ड में लगभग 300000 किमी०।

प्रश्न 7.
पृथ्वी से निकटतम तारे का नाम क्या है?
उत्तर :
सूर्य।

प्रश्न 8.
किन-किन ग्रहों के चारों ओर वलय पाया जाता है?
उत्तर :
शनि एवं यूरेनस।

प्रश्न 9.
सौर परिवार के किस ग्रह के सबसे अधिक उपग्रह पाये जाते हैं?
उत्तर :
शनि।

प्रश्न 10.
सौर परिवार के ग्रहों की संख्या बताओ।
उत्तर :
नौ।

प्रश्न 11.
सूर्य के सबसे नजदीक स्थित ग्रह का नाम क्या है?
उत्तर :
बुध।

प्रश्न 12.
सूर्य से सबसे अधिक दूरी पर स्थित ग्रह का नाम बताओ।
उत्तर :
वरुण।

प्रश्न 13.
सौरमंडल के सबसे बड़े ग्रह का नाम क्या है?
उत्तर :
वृहस्पति।

प्रश्न 14.
सूर्य से दूरी के क्रम में पृथ्वी का स्थान क्या है?
उत्तर :
तीसरा।

प्रश्न 15.
पृथ्वी के एक मात्र उपग्रह का नाम बताओ।
उत्तर :
चन्द्रमा।

प्रश्न 16.
सूर्य हमारी पृथ्वी से कितना गुना बड़ा है?
उत्तर :
13 लाख गुना।

प्रश्न 17.
सूर्यास्त के बाद आकाश में पश्चिम की तरफ दिखाई देने वाले सबसे उज्ज़्वल ज्योतिष्क का नाम क्या है?
उत्तर :
संध्या तारा।

प्रश्न 18.
ग्रहों को प्रकाश कहाँ से प्राप्त होता है?
उत्तर :
सूर्य से।

प्रश्न 19.
सौर परिवार के एक अनोखे ग्रह का नाम बताओ जहाँ केवल जीवन है?
उत्तर :
पृथ्वी।

प्रश्न 20.
सौर मंडल के ग्रह किसकी परिक्रमा करते हैं?
उत्तर :
सूर्य की।

प्रश्न 21.
सौर परिवार के सबसे गर्म ग्रह का नाम बताओ।
उत्तर :
बुध।

प्रश्न 22.
किस ग्रह के उपग्रह सबसे अधिक हैं?
उत्तर :
शनि।

प्रश्न 23.
वृहस्पति के सबसे बड़े उपग्रह का नाम बताओ।
उत्तर :
गैनीमिड।

प्रश्न 24.
सूर्य से पृथ्वी की औसतन दूरी क्या है?
उत्तर :
लगभग 15 करोड़ किमी०।

प्रश्न 25.
सौरमंडल के किस ग्रह को लाल ग्रह कहते हैं?
उत्तर :
मंगल ग्रह को।

प्रश्न 26.
चन्द्रमा किस ग्रह का उपग्रह है?
उत्तर :
पृथ्वी का।

प्रश्न 27.
पृथ्वी की एक परिक्रमा पूरा करने में चन्द्रमा को कितना समय लगता है?
उत्तर :
27 दिन 4 घण्टा।

प्रश्न 28.
ज्योतिष विज्ञानियों ने प्लूटो को सौरमंडल के छोटे ग्रह की संज्ञा कब दी?
उत्तर :
2006 ई० में।

प्रश्न 29.
महाकाश में जाने वाले को किस नाम से पुकारते हैं?
उत्तर :
अंतरिक्ष यात्री।

प्रश्न 30.
महाकाश में जाने वाले प्रथम प्राणी कौन सा है?
उत्तर :
लायका नामक कुत्ता।

प्रश्न 31.
महाकाश में जाने वाले प्रथम व्यक्ति का नाम क्या है?
उत्तर :
मेजर गैगरिन।

प्रश्न 32.
भारत की प्रथम महिला अंतरिक्ष यात्री कौन थी?
उत्तर :
कल्पना चावला।

प्रश्न 33.
भारत के प्रथम पुरुष अंतरिक्ष यात्री का नाम बताओ।
उत्तर :
राकेश शर्मा।

प्रश्न 34.
अपोलो- 11 ने कब उड़ान भरी थी?
उत्तर :
16 जुलाई, 1969 को।

प्रश्न 35.
सर्वप्रथम चन्द्रमा पर पैर रखने वाले अंतरिक्ष यात्रियों के नाम बताओ।
उत्तर :
नील आर्मस्ट्रांग और एडविन आल्ड्रिन।

प्रश्न 36.
महाकाश में स्थित छाया पथ को किस नाम से पुकारते हैं?
उत्तर :
आकाश गंगा।

प्रश्न 37.
सूर्य के सबसे निकटवर्ती नक्षत्र का क्या नाम है?
उत्तर :
प्रक्सिमा सेनेटोरी।

प्रश्न 38.
महाकाश में जाने के लिए जिस सूट की आवश्यकता होती है, उसे किस नाम से जाना जाता है?
उत्तर :
स्पेस सूट।

प्रश्न 39.
तारों का निर्माण कैसे होता है?
उत्तर :
नीहारिका से।

संक्षिप्त प्रश्नोत्तर (Brief Answer Type) : 3 MARKS

प्रश्न 1.
छाया पथ किसे कहते हैं?
उत्तर :
लाखों लाख तारों एवं नक्षत्रों से छाया पथ (Galaxy) का निर्माण होता है। सूर्य पृथ्वी और असंख्य ग्रहों को मिलाकर एक आकाश गंगा (Milky Way) का निर्माण हुआ है। छाया पथों की आकृति घुमावदार, गोलाकार इत्यादि कई तरह की होती हैं। लगभघ 10 हजार करोड़ नक्षत्र, धूलकण, गैस से बनी आकाश गंगा एक विराट घुमावदार छाया पथ है।

प्रश्न 2.
निहारिका किसे कहते हैं?
उत्तर :
आकाश गंगा में दिखाई पड़ने वाले विशाल तथा विस्तृत संपीड़ित धूल कणों तथा अत्यधिक गर्म गैस (हाइड्रोजन) के बादल जिनसे नक्षत्र या तारा एवं नक्षत्रमंडलों का जन्म होता है, उसे निहारिका कहते हैं।

प्रश्न 3.
आलोक वर्ष से तुम क्या समझते हो?
उत्तर :
जैसा कि हम जानते हैं कि सूर्य से पृथ्वी तक प्रकाश पहुँचने में 4 मिनट 20 सेकेण्ड का समय लगता है। अर्थात् प्रकाश का वेग 1 सेकेण्ड में लगभग 300000 किमी० है। इसी वेग से 1 वर्ष में प्रकाश जितनी दूरी तय करता है, उसे ही हम आलोक वर्ष (Light Year) कहते हैं।

प्रश्न 4.
तारामंडल किसे कहते हैं?
उत्तर :
एक दूसरे के नजदीक स्थित तारों को एक नक्षत्रमंडल या तारामंडल (Constellation) कहते हैं।

प्रश्न 5.
सौर परिवार से तुम क्या समझते हो?
उत्तर :
आकाश गंगा में उपस्थित करोड़ों तारों के मध्य में स्थित हल्केपीले रंग का चमकता तारा सूर्य है। सूर्य के चारों ओर ग्रह, उपग्रह, ग्रहपूँज, उल्का, धूमकेतु आदि परिक्रमा करते रहते हैं। साथ ही साथ कई तरह के गैस एवं धूलकण भी तैरते रहते हैं। इन सभी को मिलाकर सौर जगत या सौर परिवार का निर्माण होता है। इसी से इन्हें सौर परिवार कहते हैं।

प्रश्न 6.
उत्पत्ति के अनुसार सौर परिवार के सभी ग्रहों के नाम लिखो।
उत्तर :
सौर परिवार में कुल नौ ग्रह हैं, जो सूर्य से दूरी के अनुसार क्रमशः बुध(Murcury), शुक्र (Venus), पृथ्वी (Earth), मंगल (Mars), वृहस्पति (Jupiter), नेष्पून या वरुण (Naptune) तथा प्लूटो या यम (Pluto) हैं। सूर्य की तुलना में ये सभी ग्रह छोटे होते हैं एवं प्रत्येक ग्रह में अपनी गुरुत्वाकर्षण शक्ति होती है।

प्रश्न 7.
उपग्रह किसे कहते हैं?
उत्तर :
उपग्रह (Satellites) : ग्रहों की परिक्रमा करने वाले अपेक्षाकृत छोटे गोलाकार पिण्डों को उपग्रह कहते हैं। उपग्रहों का जन्म ग्रहों से हुआ है। उपग्रहों में अपना स्वय का प्रकाश एवं ताप नहीं होता है। अत: ये सूर्य के प्रकाश से ही प्रकाशित होते हैं ।

प्रश्न 8.
ग्रह किसे कहते हैं?
उत्तर :
ग्रह (Planets) : ग्रह का अर्थ है, घुमनेवाला (Wanderer) । सूर्य के चारों ओर चक्कर लगाने वाले गोलाकार पिण्डों को ग्रह कहते हैं। ग्रहों की उत्पत्ति सूर्य से हुई है। ग्रहों में अपना स्वयं का प्रकाश एवं ताप नहीं होता है। अत: ये सूर्य के प्रकाश से प्रकाशित होते हैं । इसीलिए ग्रहों का प्रकाश स्थिर होता है और ये टिमटिमाते नहीं हैं।

प्रश्न 9.
चन्द्रकला क्या है?
उत्तर :
अमावस्या से पूर्णिमा और पूर्णिमा से अमावस्या तक चाँद छोटा-बड़ा होता रहता है। अत: इस क्रिया को चन्द्रकला कहते हैं। एक पूर्णिमा से दूसरी पूर्णिमा तक के समय को चन्द्रमास कहते हैं।

प्रश्न 10.
धूमकेतू से तुम क्या समझते हो?
उत्तर :
धूमकेतु (Comets) : लम्बी पूँछ के समान उज्ज्वल ज्योतिष्क को धूमकेतु (Comets) कहा जाता है। सूर्य के पास आने पर धूमकेतु के धूल, गैस जलना शुर कर देता है जिससे यह पूँछ या दूम के समान एक आकृति बनाती है।

विस्तृत उत्तर वालें प्रश्न (Detailed Answer Questions) : 5 MARK

प्रश्न 1.
नक्षत्र किसे कहते हैं?
उत्तर :
नक्षत्र या तारे (Stars) : वे आकाशीय पिण्ड जिनमें अपना स्वयं का प्रकाश एवं ताप होता है, उन्हें नक्षत्र या तारा कहते हैं। इनका प्रकाश स्थिर न होकर घटता-बढ़ता है। अर्थात् ये टिमटिमाते हैं। पृथ्वी से अधिक दूरी पर स्थित होने के कारण ये तारे हमें प्रकाश बिन्दु की तरह अत्यन्त छोटे दिखाई पड़ते हैं।

प्रश्न 2.
स्पेस सूट क्या है?
उत्तर :
महाकाश में जाने के लिए जिस पोशाक की आवश्यकता होती है, उसे स्पेश सूट कहते हैं। इस सूट के अन्दर हवा भरी होती है एवं यह इस प्रकार से तैयार किया हुआ होता है कि इसके ऊपर महाकाश की कोई रश्मि अपना प्रभाव नहीं डाल पाती है, जिससे अंतरिक्ष यात्रियों को कोई क्षति नहीं होती है एवं वे सुरक्षित रहते हैं।

प्रश्न 3.
स्पेस सटल किसे कहते हैं?
उत्तर :
राकेट द्वारा अंतरिक्ष में जाया जा सकता है। लेकिन सुरक्षित रूप से पुन: वापस पृथ्वी पर आया नहीं जा सकता है। अत: इस समस्या के समाधान के लिए जिस साधन का प्रयोग किया जाता है ताकि अंतरिक्ष यात्रियों को सुरक्षित पृथ्वी पर पुन: उतारा जा सके उसे स्सेस शटल या महाकाश विमान कहते हैं।

प्रश्न 4.
चन्द्रमा से आप क्या समझते हैं? स्पष्ट कीजिए।
उत्तर :
चन्द्रमा (Moon) : चन्द्रमा पृथ्वी का एकमात्र उपग्रह (Satellite) है। पृथ्वी से इसकी दूरी लगभग 3 लाख 84 हजार किमी० है एवं इसका आकार पृथ्वी के आकार का … भाग है। चन्द्रमा की उत्पत्ति के सम्बन्ध में विद्वानों की यह धारणा है कि सूर्य से अलग होने पर कई वर्षों के बाद भी पृथ्वी तरल एवं गैसीय अवस्था में थी, इसलिए सूर्य के आकर्षण के कारण पृथ्वी पर ज्वार आया जिससे पृथ्वी का कुछ भाग टूटकर पृथ्वी से अलग हो गया जो बाद में चन्द्रमा के रूप में पृथ्वी की परिक्रमा करने लगा। पृथ्वी की एक बार परिक्रमा पूरा करने में चन्द्रमा को 27 दिन 4 घण्टे का समय लगता है। चन्द्रमा की आवर्तन गति और परिक्रमा की गति में लगभग एक जैसा ही समय लगता है। इसी कारण पृथ्वी से चन्द्रमा का एक ही भाग हमेशा दिखाई देता है।

प्रश्न 5.
सौर तृफान क्या है?
उत्तर :
सौर तूफान (Solar Storm) : सूर्य के बाहरी स्तर पर छोटेछोटे विस्फोट होने से पर्याप्त परिमाण में आयनित कण, गैस, रश्मि चारों ओर गिरने लगती है। इसे ही सौर तूफान (Solar Storm) कहते हैं। ऐसा वैज्ञानिकों का मानना है कि हर 11 वर्षों के बाद या अन्तराल पर ऐसे तूफान आते हैं जिसके कारण पृथ्वी पर कृत्रिम उपग्रह संपर्क व्यवस्था पर प्रभाव पड़ता है।

प्रश्न 6.
ग्रहण पूँज (क्षूद्र तारा) किसे कहते हैं?
उत्तर :
महाकाश में ग्रह की तरह ही छोटे-छोटे ज्योतिष्क (ग्रहण) निर्दिष्ट अपने कक्ष पथ पर सूर्य के चारों तरफ परिक्रमा करते रहते हैं। इसी छोटे-छोटे ज्योतिष्क को ग्रहण पूँज कहते हैं।

प्रश्न 7.
उल्का से आप क्या समझते हैं?
उत्तर :
उल्का (Meteoraids) : मेघहीन स्वच्छ आकाश में रात्रि के समय अचानक ही एक प्रकाश की रेखा देखी जाती है। ऐसा लगता है मानो आकाश में प्रकाश की एक लकीर नीचे की तरफ खिंची हो। अतः इसे तारा खसा या तारों का टूटना कहते हैं। वास्तव में यह उल्का पिण्ड है। धूमकेतु ग्रहण पूँज से टूटे हुए छोटे-छोटे टुकड़े आकाश में घूमते रहते हैं एवं पृथ्वी की आकर्षण शक्ति के कारण प्रचण्ड वेग से पृथ्वी की तरफ आते हैं।

प्रश्न 8.
कृत्रिम उपग्रह किसे कहते हैं?
उत्तर :
कृत्रिम उपग्रह : मनुष्य के द्वारा बनाये गये यंत्र जो पृथ्वी के चारों तरफ घूमते हैं, इन्हें कृत्रिम उपग्रह कहते हैं। अनेक देशों ने अंतरिक्ष में उपग्रहों को भेजा है। यह कृत्रिम उपग्रह अनेक जानकारियाँ देती है। जैसे- मौसम का पूर्वाभास, समुद्र परिवहन, प्राकृतिक विपदा के पूर्व सतर्कता एवं महाकाश गवेषणा आदि मुख्य हैं।

प्रश्न 9.
पृथ्वी पर ही जैव जगत संभव है, क्यों?
उत्तर :
सौर परिवार के सभी ग्रहों में पृथ्वी सबसे महत्वपूर्ण एवं अनुपम है। यह सूर्य से न तो काफी नजदीक है और न ही काफी दूर स्थित है। अतः पृथ्वी पर तापक्रम उपयुक्त रहता है। इसलिए सभी ग्रहों में केवल पृथ्वी पर ही जीवन संभव है। इसके अलावा अन्य किसी ग्रह पर जीवन सम्भव नहीं है। जीवन के लिए जल और वायु का होना आवश्यक है। जल एवं वायु केवल पृथ्वक्म पर ही पाया जाता है। इसलिए सभी ग्रहों में पृथ्वी ही एकमात्र ग्रह है जिस पर जीवन संभव है।

बहुविकल्पीय प्रश्नोत्तर (Multiple Choice Question & Answer) : (1 Mark)

प्रश्न 1.
ब्रह्माण्ड में चमकने वाले सभी आकाशीय पिण्डों को कहते हैं-
(a) ग्रह
(b) ज्योतिष्क
(c) निहारिका
(d) चन्द्र
उत्तर :
(b) ज्योतिष्क

प्रश्न 2.
छोटे एवं लाल तारे की उष्णता होती है-
(a) सबसे कम
(b) सबसे अधिक
(c) इनमें से कोई नहीं
(d) कम
उत्तर :
(a) सबसे कम

प्रश्न 3.
मध्य एशिया में सप्तर्षिमंडल को कहते हैं-
(a) खूँटी में बँधे मेमने
(b) खूँटी में बँधे घोड़े
(c) खूँटी में बँधे बैल
(d) खूँटी में बँधी बकरी
उत्तर :
(b) खूँटी में बँधे घोड़े

प्रश्न 4.
उत्तरी आसमान का ध्रुवतारा है-
(a) मद्धिम
(b) चमकीला
(c) कोई नहीं
(d) इनमें से कोई नहीं
उत्तर :
(a) मद्धिम

प्रश्न 5.
सूर्य हमारी पृथ्वी से बड़ा है-
(a) 14 लाख गुना
(b) 13 लाख गुना
(c) 20 लाख गुना
(d) 10 लाख गुना
उत्तर :
(b) 13 लाख गुना

प्रश्न 6.
सूर्य का व्यास है-
(a) 14 लाख किलोमीटर
(b) 22 लाख किलोमीटर
(c) 5 लाख किलोमीटर
(d) 10 लाख किलोमीटर
उत्तर :
(a) 14 लाख किलोमीटर

प्रश्न 7.
सूर्य की ऊपरी सतह का तापक्रम है-
(a) 6000° C
(b) 4000° C
(c) 1800° C
(d) 5000° C
उत्तर :
(a) 6000° C

प्रश्न 8.
सूर्य और पृथ्वी के बीच की दूरी है-
(a) 80 करोड़ किमी०
(b) 7 लाख किमी०
(c) 15 करोड़ किमी०
(d) 8 हजार किमी०
उत्तर :
(c) 15 करोड़ किमी०

प्रश्न 9.
सूर्य के ताप का केवल ….. भाग ही पृथ्वी तक पहुँचता है-
(a) अरब वाँ भाग
(b) 1 / 12 लाख वाँ भाग
(c) इनमें से कोई नहीं
(d) करोड़ वाँ भाग
उत्तर :
(a) अरब वाँ भाग

प्रश्न 10.
सूर्य के बाद पृथ्वी का निकटतम तारा है-
(a) अल्फा सेनटोरी
(b) बुध
(c) इनमें से कोई नहीं
(d) मंगल
उत्तर :
(a) अल्फा सेनटोरी

प्रश्न 11.
हमारी पृथ्वी के उपग्रहों की संख्या है-
(a) 3
(b) 1
(c) 11
(d) 12
उत्तर :
(b) 1

प्रश्न 12.
मंगल ग्रह के उपग्रहों की संख्या है-
(a) 1
(b) 3
(c) 2
(d) 5
उत्तर :
(c) 2

प्रश्न 13.
मंगल और वृहस्पति के बीच ग्रहण पूँज देखे जाते हैं-
(a) 5000
(b) 40000
(c) 10000
(d) 20000
उत्तर :
(b) 40000

प्रश्न 14.
मंगल ग्रह की सतह है-
(a) नीला
(b) पीला
(c) लाल
(d) हरा
उत्तर :
(c) लाल

प्रश्न 15.
अंतरिक्ष से पृथ्वी किस रंग की दिखाई देती है-
(a) नीला
(b) काला
(c) भूरा
(d) पीला
उत्तर :
(a) नीला

प्रश्न 16.
वृहस्पति ग्रह हमारे सौरमंडल का ग्रह है-
(a) छोटा
(b) सबसे बड़ा
(c) सबसे नजदीक
(d) सबसे छोटा
उत्तर :
(b) सबसे बड़ा

प्रश्न 17.
सौरमंडल का सबसे छोटा ग्रह है-
(a) बुध
(b) शुक्र
(c) पृथ्वी
(d) चन्द्र
उत्तर :
(a) बुध

प्रश्न 18.
सूर्य से सबसे अधिक दूरी पर स्थित ग्रह है-
(a) वरुण
(b) बुध
(c) प्लूटो
(d) शुक्र
उत्तर :
(c) प्लूटो

प्रश्न 19.
प्लूटो को सूर्य की परिक्रमा करने में समय लगता है-
(a) 3 महीना
(b) 248 वर्ष
(c) 12 वर्ष
(d) 246 वर्ष
उत्तर :
(b) 248 वर्ष

प्रश्न 20.
सौर परिवार का सबसे गर्म ग्रह है-
(a) शुक्र
(b) बुध
(c) मंगल
(d) प्लूटो
उत्तर :
(b) बुध

प्रश्न 21.
अंतरिक्ष में जाया जाता हैं –
(a) हेलिकॉप्टर से
(b) रॉकेट से
(c) हवाई जहाज से
(d) इनमें से कोई नहीं
उत्तर :
(b) रॉकेट से

प्रश्न 22.
शनि के उपग्रह हैं-
(a) 20
(b) 23
(c) 27
(d) 24
उत्तर :
(b) 23

प्रश्न 23.
सौर परिवार का सबसे ठंडा ग्रह है-
(a) पृथ्वी
(b) प्लूटो
(c) मंगल
(d) शुक्र
उत्तर :
(b) प्लूटो

रिक्त स्थानों की पूर्ति करो (Fill in the blanks) : (1 Mark)

1. नक्षत्रों में अपना ________ होता है।
उत्तर : प्रकाश

2. ग्रहों में अपना ________ नहीं होता है।
उत्तर : प्रकाश

3. ________ का एक मात्र उपग्रह चन्द्रमा है।
उत्तर : पृथ्वी

4. सौरमंडल का सबसे बड़ा ग्रह ________ है।
उत्तर : वृहस्पति

5. आकाश की उत्तर दिशा में ज्ञात उज्वल तारों के समूह का ________ कहते हैं।
उत्तर : सप्तर्षिमंडल

6. धुवतारा हमेशा आकाश में ________ दिशा में दिखाई पड़ता है।
उत्तर : उत्तर

7. बुध ग्रह सूर्य के सबसे ________ का ग्रह है।
उत्तर : नजदीक

8. सूर्य एवं पृथ्वी के बीच की दूरी ________ किमी० है।
उत्तर : 15 करोड़

9. सूर्य का बाह्य ताप्र लगभग ________ है।
उत्तर : 6000° C

10. पृथ्वी से सूर्य ________ लाख गुना बड़ा है।
उत्तर : 13

11. पृथ्वी से सूर्य ________ लाख गुना भारी है।
उत्तर : 3

12. हमें खुली आँखों से ________ को नहीं देखना चाहिए।
उत्तर : सूर्य

13. ग्रहों में अपना प्रकाश और ________ नहीं होता है।
उत्तर : ताप

14. सौर परिवार के ग्रहों को प्रकाश और ताप ________ से प्राप्त होता है ।
उत्तर : सूर्य

15. पृथ्वी से चन्द्रमा ________ किमी० दूर है।
उत्तर : 3.84 लाख

16. सूर्य के बाद पृथ्वी का निकटतम तारा ________ है।
उत्तर : अल्फा सेनटोरी

17. मंगल ग्रह की सतह ________ है।
उत्तर : लाल

18. अंतरिक्ष से पृथ्वी ________ रंग की दिखाई देती है।
उत्तर : नीले

19. सौरमंडल का सबसे बड़ा ________ उपग्रह है।
उत्तर : टाइटन

20. यूरेनस ________ दिशा में सूर्य की परिक्रमा करता है।
उत्तर : घड़ीवत्

21. ब्रिटेन द्वारा खोजे गये ग्यारहवें ग्रह का नाम ________ है।
उत्तर : पोडिशन

22. बुध सौरमंडल का सबसे ________ ग्रह है।
उत्तर : गर्म।

सही एवं गलत का निर्णय करो : True or False (1 mark)

1. आकाशीय पिण्डों को ज्योतिष्क कहा जाता है।
उत्तर : (सही)

2. हमारी पृथ्वी के चारों तरफ वायुमंडल पाया जाता है।
उत्तर : (सही)

3. ग्रहों में अपना स्वयं का प्रकाश व ताप होता है।
उत्तर : (सही)

4. प्लूटो सौरमंडल का सबसे गर्म ग्रह है।
उत्तर : (सही)

5. तारा आकाश में देखने में छोटे लगते हैं परन्तु वास्तव में छोटे नहीं हैं।
उत्तर : (गलत)

6. ग्रहों का आकार सूर्य से बहुत छोटा होता है।
उत्तर : (सही)

7. मिथेन गैस की अधिकता के कारण यूरेनस ग्रह का रंग नीला दिखाई पड़ता है।
उत्तर : (सही)

8. शनि ग्रह के 27 उपग्रह हैं।
उत्तर : (गलत)

9. सेरेस सौरमंडल का सबसे छोटा ग्रह पूंज है।
उत्तर : (गलत)

10. भारत का सर्वप्रथम कृत्रिम उपग्रह आर्यभट्ट है।
उत्तर : (गलत)

11. कल्पना चावला भारत की प्रथम महिला अंतरिक्ष यात्री है।
उत्तर : (सही)

12. हमें पृथ्वी से चन्द्रमा का एक भाग ही दिखाई देता है।
उत्तर : (सही)

13. मंगल ग्रह के एक भाग में सदा दिन एवं दूसरे भाग में सदा रात रहती है।
उत्तर : (सही)

14. सोवियत संघ द्वारा खोजे गये दशवें ग्रह का नाम भालकन है।
(गलत)

15. चन्द्रमा के सतह पर कई जलरहित गड्दे पाये जाते हैं।
उत्तर : (सही)

16. चन्द्रमा की व्यास 3475 किलोमीटर है।
उत्तर : (सही)

17. चन्द्रमा पृथ्वी की एक परिक्रमा 27 \(\frac{1}{3}\) दिन में पूरा कर लेता है।
उत्तर : (सही)

18. प्लूटो सौरमंडल का सबसे ठंडा ग्रह है।
उत्तर : (सही)

19. नेप्यून सौरमंडल का तीसरा सबसे बड़ा ग्रह है।
उत्तर : (गलत)

20. सूर्य के ताप का केवल अरब वाँ भाग ही पृथ्वी तक पहुँचता है।
उत्तर : (सही)

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 8 Pollution offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 8 Question Answer – Pollution

Answer the following questions briefly: (1 mark each)

Question 1.
What is the main source of air pollution?
Answer:
Auto-vehicles

Question 2.
Name a natural source of air pollution.
Answer:
Volcanic eruption

Question 3.
Name a man-made source of air pollution.
Answer:
Industrialisation

Question 4.
Expand CFCs.
Answer:
Chloro fluoro carbons

Question 5.
Which gases deplete ozone layer?
Answer:
CFCs

Question 6.
Name a disease caused by air pollution.
Answer:
Lung cancer

Question 7.
Which element causes acid rain?
Answer:
Sulphur

Question 8.
Which gas is called Greenhouse gas?
Answer:
Carbon dioxide

Answer the following questions briefly: (2 mark each)

Question 1.
Define pollution and its types.
Answer:
Pollution : Pollution is defined as the contamination of natural environment that causes instability, disorder, harm to the ecosystem i.e. physical systems or living organisms.

Types of Pollution :

• Air pollution
• Water pollution
• Land pollution
• Noise pollution.

Question 2.
What are pollutants?
Answer:
Elements which cause pollution and harm the ecosystem are called pollutants.

Question 3.
How is acid rain caused?
Answer:
Acid rain : Acid rain is caused mainly by the presence of oxides of sulphur and nitrogen in the upper atmosphere, where the rain precipitation occurs.

Question 4.
Name the causes and effects of air pollution.
Answer:
Causes and effects of air pollution are –

• greenhouse effect
• particulate, contamination
• increased UV radiation
• acid rain
• increased ground level ozone concentration
• increased levels of nitrogen oxides.

Question 5.
What is radiation pollution?
Answer:
Radiation pollution is caused by radioactive substances released by nuclear power plants. This is harmful to humans and other organisms.

Question 6.
Name two greenhouse gases.
Answer:
Carbon dioxide, methane.

Question 7.
What is smog ?
Answer:
In urban areas smog is formed when fog is mixed with smoke,

Question 8.
How is depletion of ozone caused ?
Answer:
Depletion of ozone is caused mainly by chlorofluorocarbons (CFCs) emitted from air conditioners refrigerators etc.

Question 9.
Name the important gases which is responsible for ‘greenhouse effect’?
Answer:
Chlorofluorocarbons (CFCs) and carbon dioxide.

Question 10.
Write any one cause of indoor air pollution.
Answer:
Chemicals like paints, varnishes etc, artificial building materials like plywood can cause indoor pollution. Poor ventilation is homes can worsen the situation.

Question 11.
How air polluted by different automobiles?
Answer:
Buses, lorries, private cars, ships and aeroplanes use petrol, diesel, gasoline as fuels. As a result huge amounts of lead and carbon monoxide gets mixed with air.

Question 12.
How air polluted by bacteria repellents and air fresheners?
Answer:
Air also gets polluted from the waste, the smoke of incense sticks, mosquito coils and oils, chemical substances used as bacteria repellents and air fresheners.

Answer the following questions briefly: (3 mark each)

Question 1.
Describe the harmful effects of air pollution on human body.
Answer:
Harmful effects of air pollution :

• Inhalation of polluted air causes diseases associated with respiratory system.
• It ranges from common cold to lung cancer.
• Damage to respiratory system may lead to bronchitis, asthma etc.
• Air polluted with carbon monoxide, when inhaled reacts with hemoglobin of blood and reduces its oxygen-carrying capacity.
• Some pollutants in air also cause irritation to eyes.

Question 2.
What is the cause of depletion of ozone layer?
Answer:
The continous use of chlorofluoro carbons (CFCs) as refrigerants, coolants, propellants in aerosol sprays, discharge of oxides of nitrogen from supersonic aircrafts, excessive use of nitrates as fertilizers deplete the ozone layer. This results in the increase in ultraviolet radiation from the sun reaching the earth.

Question 3.
Explain Green house effect.
Answer:
Atmosphere consists of different types of gases namely nitrogen, oxygen, carbon dioxide and other gases. Out of all gases, carbon dioxide has the tendency to retain or trap heat radiated from the earth’s surface. As the concentration of carbon dioxide increases in the atmosphere, more and more heat gets trapped.

Carbon dioxide is transparent to incoming solar radiation but does not allow long wave terrestrial radioations to escape into the space. This causes the temperature of earth to rise. This is called greenhouse effect.

Question 4.
State measures for abatement of air pollution.
Answer:

• Air quality standards be used.
• Technical division for industries be used.
• Vehicular exhaust be controlled.
• CFC free products are to used.
• Alternative products be used.

Identify the correct answers (MCQ): (1 mark each)

Question 1.
Which one of the following air pollutants is formed by the burning of coal ?
a. Sulphur dioxide
b. Ammonia
c. Nitrogen dioxide
d. Nitric acid.
Answer:
a. Sulphur dioxide

Question 2.
Which gas is both harmful and beneficial to life on earth ?
a. Oxygen
b. Ozone
c. Carbon dioxide
d. Methane
Answer:
b. Ozone

Question 3.
Which is the major source of harmful radiations in the house?
a. Tube light
b. Colour TV
c. Microwave oven
d. Heater
Answer:
b. Colour TV

Question 4.
Which gas is mainly responsible for the creation of the Greenhouse effect?
a. Ozone
b. Oxygen
c. Carbon dioxide
d. Carbon monoxide
Answer:
c. Carbon dioxide

Question 5.
Of the following four metropolitan cities, tell where pollution hangs above like a cloud ?
a. Mumbai
b. Kolkata
c. Delhi
d. Chennai
Answer:
c. Delhi

Question 6.
Which colour has become established as a sign of conservation and environment ?
a. Orange
b. Purple
c. Safron
d. Green
Answer:
d. Green

Question 7.
Green house effect is-
a. an ocean phenomenon
b. atmospheric phenomenon
c. soil phenomenon
d. none of these.
Answer:
b. atmospheric phenomenon

Question 8.
Which day is celebrated as world environment day?
a. 2 February
b. 19 July
c. 5 June
d. 28 August
Answer:
b. 19 July

Question 9.
Depletion of ozone is caused by ………………..
a. water pollution
b. air pollution
c. land pollution
d. noise pollution.
Answer:
b. air pollution

Question 10.
Acid rain is likely to occur in ………………..
a. desert
b. a highly industrialised a tea
c. a forest area
d. agricultural area.
Answer:
d. agricultural area.

Question 11.
A warm layer of air over a cool, stationary layer of air is scientifically called ………………..
a. Smog
b. Fog
c. Thermal pollution
d. Thermal inversion.
Answer:
b. Fog

Question 12.
Acid rain is a serious problem in …………………
a. Cape Town
b. New York
c. Rome
d. Chandigarh
Answer:
c. Rome

Question 13.
Major pollutant for ozone depletion is ………………..
a. water vapour
b. dust
c. chlorofluorocarbons
d. vapour
Answer:
b. dust

Question 14.
Ozone layer is found over a distance of ………………..
a. 5-6 km
b. 10-35 km
c. 55-75 km
d. 40-100 km
Answer:
a. 5-6 km

Question 15.
Preventive measure for air pollution
a. controlled use of fossil fuels
b. control of air pollution
c. built of damage
d. none of these
Answer:
b. control of air pollution

Fill in the blanks with correct words : (1 mark each)

1. In urban area ____ is formed when fog is mixed with smoke.
Answer: smog

2. Major pollutant for ozone depletion is ____
Answer: chlorofluorocarbons

3. Global warming is caused by ____ effect.
Answer: Greenhouse

4. CFC is the main threat to ____ layer.
Answer: ozone

5. Forest fire causes ____ to mix with air.
Answer: carbon dioxide

6. Decomposition of swampy land and bogs emits ____ gas and pollutes air.
Answer: methane

7. ____ pollution may be defined as an unwanted change in the quality of the earth’s atmosphere.
Answer: Air

8. The ____ layer of the earth’s atmosphere protects us from the harmful ultraviolet rays of the sun.
Answer: ozone

9. Many marble statues are damaged due to ____ caused as a result of air pollution.
Answer: acid rain

10. Ultraviolet rays are responsible for cancer of ____ and ____ in human beings.
Answer: skin, eyes

If the sentence is true, write ‘T’ and if false write ‘F’ against the following :

1. CFC is a greenhouse gas.
Answer: True

2. Afforestation can same the grave situation of the environmental pollution.
Answer: True

3. Air pollution is caused by poisonous gases like carbon dioxide, carbon monoxide, nitrogen oxide, sulphur dioxide etc.
Answer: True

4. The amount of carbon dioxide in air is decreasing day by day.
Answer: False

5. Ozone hole is largest over Antarctica.
Answer: True

Match the Following (1 mark each)

1. Smog	a. damages marble statues
2. Global warming	b. winter morning
3. CFC	c. melting of polar ice cap
4. Acid rain	d. disease caused by air pollution
5. Asthma	e. Greenhouse gas

Answer:

1. Smog	b. winter morning
2. Global warming	c. melting of polar ice cap
3. CFC	e. Greenhouse gas
4. Acid rain	a. damages marble statues
5. Asthma	d. disease caused by air pollution

Pollution Class 6 WBBSE Notes

Chapter at a Glance

• Pollution : Pollution is defined as the contamination of natural environment.
• Pollutants : Substance that contaminate air.
• Anthropogenic pollutant : Pollutants such as carbon dioxide, emitted due to burning of fossil fuels.
• Aerosols : Matter emited into the air-like dust, smoke, mist, fog.
• Acid rain : Acid rain is caused when a pollutant like sulphuric acid combines with droplets of water in the air.
• Smog : Smog is smoke and fog emitted in industrial forms

Causes of Air Pollution : Air pollution is caused by harmful gases such as carbon dioxide, sulphur dioxide and nitrogen dioxide and very small particles of carbon. Most of the air pollution is caused by the emissions factories, vehicles and livestocks. Environment is our basic life support system. It provides the air we breath, the water we drink, the food we eat and the land where we live.

How do human beings modify this natural environment? The car fumes pollute the air, water is collected in a pot, food is served in vessels and land is used to build factories. Human beings make cars, mills factories and manufacture containers. This is how human beings modify natural environment then what is environment? What ever we see in our surroundings is a part of our environment. Everything which surrounds us may collectively be termed as the environment.

Modern man lives a life of comfort and luxury which requires additional resources. The activity of modern man has slowly degrading the quality of global environment. So life on this planet earth has continued to modify and alter the atmospheric, lithospheric and oceanic components of the natural environment since the very beginning. As a result, the changed environmental conditions adversely affect the organisms in the biosphere. This deteriorating conditions of the physical environment is called environmental degradation.

What is Pollution ? Pollution is defined as the contamination of natural environment that causes instability, disorder, harm to the ecosystem i.e. physical systems or living organisms.

Pollution means the presence of undesirable substance in any segment of the environment primarily due to human activity discharging by products and waste products which are harmful to man and other organisms. The environmental pollution is now considered a global phenomenon.

What is pollutant? A pollutant is defined as any form of energy or matter that causes degradation and pollution.

Different types of Pollutants : Pollutants can be divided into following types-

• Primary pollutants such as carbon monoxide
• Secondary pollutants such as ozone, aerosols
• Biodegradable pollutants such as sewage
• Nonbiodegradable pollutants such as plastics
• Natural pollutants such as carbon dioxide.

Air Pollution :

Definition : Air pollution may be defined as the mixing of some substances in the surrounding (ambient) air in such concentration that a situation arises in which man and environment is badly affected. It is an unwanted change in the quality of the earth’s atmosphere caused by emission of gases due to burning of fossil fuels and other natural causes.

Causes of air pollution: Air pollution is caused by various types of pollutants released mainly from different sources or reasons. There are many causes of air pollution which may be grouped into two categories.
A. Air pollution due to natural causes and
B. Air pollution due to human activities.

A. Air pollution due to nature : The air pollutions which are caused by nature may be distinguished as :

• Volcanic eruption : It may be caused by volcanicity, when eruption occurs, sulphides, sulpher dioxide, carbon monoxide and other gases come out and mix with air, causing pollution.
• Forest fire : Forest fires caused due to friction of two dry branches release carbon dioxide, ash, carbon particles those mix with the air and pollute it.
• Dust storm : Occurence of dust storms in different parts on earth surface specially in desert are as release huge amount of dust particles in the air we breath become heavy pollution.
• Decompositions of Swampy land: Decomposition of swampy land and bogs emits methane gas and thus pollutes air.

B. Air pollution due to human activities : Increase in population, deforestation, urbanization, industrialization and wars have rapidly taken place. Air pollution is caused by various types of pollutants released mainly from industries, thermal powers, domestic appliances and automobiles.

a. Fossil fuel based industries:

• Petroleum refineries release poisonous gases like sulphur dioxide SO₂ nitrogen oxides (NO) etc.
• Large scale burning of fossil fuels such as coal, diesel, petroleum produces poisonous gases like carbon dioxide CO₂ carbon monoxide (CO), nitrogen oxide (NO) and sulphur dioxide.

b. Cement factories : Dust is produced from cement factories as stones crushers and hot mix plants release suspended particulate matter (SPM) more than five times the safety limits by industrial standards.

c. Thermal power plants : Thermal power plants produce deadly pollutants such as fly ash, SO₂ hydrocarbon etc.

d. Other industries : Other industries like food, fertilizers and chemical manufacturing plants also produce harmful poisonous gases.

Urban areas : In urban areas, automobiles are the chief sources of air pollution. The ever-increasing traffic density has aggravated the existing problem of air pollution particularly in the major cities of the world.

f. Automobiles : Automobiles mainly produce pollutants like unburnt hydrocarbons, CO (carbon monoxide), NO (nitrogen oxide), lead oxides etc. Other pollutants like aldehydes, esters, ethers, ketones and peroxides are also found in automobile emissions.

Some 10 lakhs kilograms of smoke emitted daily from the vehicles that ply on roads of the five metropolises of our country namely Kolkata, Delhi, Mumbai, Chennai and Bangaluru gets mixed with air. The chief pollutants derived from different sources are listed below :

i. Carbon compounds : Carbon compounds complete combustion of fossil fuels like mineral oil and coal produces carbon dioxide CO₂ and carbon monoxide (CO). The principal sources of CO, apart from automobiles, are combustion processes such as stones, forest fires and open fires.

ii. Sulphur compounds : Fossil fuels like coal release sulphur compounds like SO₂ hydrogen sulphide H₂ and sulphuric acid (H₂SO)₄).

Amongst all the compounds, the oxides of sulphure are considered to be the most poisonous pollutants. The other compounds include carbonyl sulphide (COS), carbon disulphide (CS₂), dimethyl sulphide [(CH₃)₂] and sulphates (XSO₄).

iii. Nitrogen Oxides (NOX) : Nitrogen monoxide (NO), nitric acid (HNO)₃ and nitrogen dioxide NO₂ are released by automobiles, industries, power plants etc.

iv. Ozone (O₃): It is released from home appliances like refrigerators, air conditioners etc. due to the release of harmful chlorofluorocarbons (CFCs), etc. (O₃) is also formed in the atmosphere as a result of chemical reactions involving polutants like SO₂, NO₂ aldehydes etc.

Others :

• Smoking of cigarettes, cigars, bidis etc. produces carbon monoxides gas due to incomplete combustion of tobacco leaves.
• Pesticides and insecticides are complex organic compounds using toxic elements like chlorine, bromine, arsenic etc. for killing pests and insects.
• Chemicals like paints, varnishes etc., artificial building materials like plywood can cause indoor pollution.
• Huge amount of smoke, carbon particles and quite a few harmful gases blend with air from the wood, cowdung cakes, coal and gas used in cooking.
• Air also gets polluted from waste, the smoke of incense sticks, mosquito coils and oils, chemical substances used as bacterial repellents and air fresheners.
• In 2011, there was an explosion in the nuclear plant at Fukushima in Japan. As a result huge amount of radioactive materials contaminated the air causing pollution.

Effects of Air Pollution
A brief discussion of the impact of air pollution follows :

1. Ozone Depletion :
What is ozonosphere :
Ozone is gas. The region of stratosphere of atmosphere, at an attitude of 23-26 km over equator and at slightly lower altitude elsewhere, having a thick sheet of ozone is called ozonosphere. As per estimates, 90% of the total atmospheric ozone is present in this region.

A What is ozone and its utility ? : Ozone is a form of oxygen. The molecule of ozone contains three oxygen atoms (O₃). In the stratosphere, ozone is being photo-dissociated and generated by the absorption of short-wave length ultraviolet UV radiations :

The two reactions (photodissociation of O₃ and its generation) are in equilibrium leading to steady concentration of ozone in the stratosphere some 20-26 km above sea level. This ozone dynamics dissipates the energy of UV radiations as heat. In this way, ozone layer in the stratosphere acts as a shield to protect all types of life on earth from the harmful effects of UV radiations.

A Unit of measurement : The amount of atmospheric ozone is measured by Dobson Spectrometer and is expressed in Dobson Units [DU]. One DU is equivalent to 0.01 mm thickness of pure ozone at the density it would possess if it were brought to ground level pressure (1 atm).

A Thickness and absorption of UV radiation : Absorption of UV radiations by ozone blanket is proportional to its thickness. As the thickness of ozone is more above poles than at equator, therefore, the maximum amount of UV radiations pass through atmosphere to reach the earth surface in the tropics (near equator).

This amount of UV radiations reaching the earth decreases towards the poles. Also, concentration of ozone in the stratosphere changes with seasons; it is maximum during spring season (February to April) and maximum during fall season (July to October).

Ozone hole : Decline in the thickness of ozone layer over a restricted area is called ozone hole. It was first discovered over Antarctica in 1985 by Dr. Joe. C. Farman and his colleagues in British Antarctic Surveys. The spring time ozone layer thickness above Antarctica varies from 280 to 325DU[1DU = 1ppb] between 1956 A. D. to 1970 A. D. Thereafter, it sharply declined to 225 DU in 1979, to 136 DU in 1985, and to about 94 DU in 1994.

Causes of ozone depletion and ozone hole : Chlorofluorocarbons (CFCs) are mainly responsible for ozone depletion in the stratosphere. CH₄ and N₂O also cause destruction of O₃ through complicated series of reactions. CFCs are a group of synthetic chemicals first discovered by Thomas Midgley Jr. in 1930. Chlorofluorocarbons are used as coolants in refrigerators and air conditioners, as propellants, cleaning solvents, slerilant and in styrofoam etc.

Once released in the troposphere, CFCs reach the stratosphere and produce ‘active chlorine’ [Cl and ClO radicals] in the presence of UV radiation. These radicals through chain reactions destroy ozone by converting it into oxygen. A single chlorine atom converts 1 lakh molecules of ozone into oxygen.

Acid Rain:
The poisonous gases and other chemicals heat power into atmosphere every second have made atmosphere a global sink of dangerous wastes. In this sink hundreds of chemical reactions are surfacing from time to time. Apart from global warming and ozone depletion acid rain is another complex phenomenon. Its effect is compounded by the fact that is occurs with precipitation. Sulphuric acid and nitric acid are produced by burning of petrol, coal and gas in automobiles and factories. They are also chief waste products of power stations.

These geses collect in atmosphere and mix with the moisture in air and fall to the ground with precipitations (rain, snow, hail). The rain clouds of ten drift hundreds of kilometre before falling as rain. The presence of carbon dioxide in air reduces rainfall pH (hydrogen ion concentration to 5.6 is water).

In industrialised countries of the world like the USA, Western Europe, North-East China and Japan acid rain with a pH below 4.0 has been recorded. Norway and Sweden also have experienced acid rain as a result of emissions in air in the UK. Much of the acid rain experienced in north-western Europe comes from emissions in atmosphere in Germany because of drifting of clouds.

3. Effects on Weather and Climate :
a. Smog: Big factories emit a lot of smoke, dust, carbon and dust particles. They pollute out atmosphere. Fog is formed during cool nights particularly in England. These particles remain in the atmosphere. Fog is then called smog. In 1952, the smog formed over London killed 4,000 persons due to suffocation.

b. Leakage of poisonous gases :

• The Leakage of poisonous gases from a pesticide factory in Bhopal in the year 1984 caused deaths to thousands of people.
• The leakage of radioactive material in Chernobyl Atomic Power Plant in Russia in 1986 resulted in extensive damage.

4. Effects on Human health
Air pollution mainly affects the respiratory system. Bronchitis, asthma and lung cancer are some of the chronic diseases caused due to exposure to polluted air.

5. Effects on Plants and Animals
Air pollution has caused widespread damage to vegetation. Depletion of ozone results in increase of ultra-violet solar radiation reaching the earth’s surface. The UV rays badly affect plant and animal communities in a variety of ways.

Green house Effect

Definition : A building
made chiefly of glass for growing or sheltering the delicate or exotic plants is called green house. The air in the greenhouse is warmer than the outside air though it receives less solar radiation. The occurrence of higher temperature inside a green house than outside, even though the interior receives less solar radiation, is known as the ‘green house effect’.

Reasons for Green House Effects: Three factors contribute to the green. house effects i.e. warmness in a green house:

• Glass wall is of the green house
  
• CO₂ contents, and
  
• Water vapour contents of the air in the green house.

These allow most of the solar radiations to enter right upto the earth’s surface, but do not allow a substantial amount of the long-wave infrared radiation emitted by the earth to escape. This makes green house air warmer than the outside air.

Green House Effect on Earth : If the earth had no atmosphere, its average surface temperature would be about -18°C, the same as that of the moon, which lacks atmosphere. Actually, the temperature of the earth’s surface is about 15°C. The reason why the earth is warmer than the moon is that it has an atmosphere.

The atmospheric cover around the earth acts like glass walls of a greenhouse. It absorbs much of the incoming solar radiation from the sun and rediates to the earth’s surface. However, it prevents the long-wave infrared radiation emitted by the earth’s surface to escape into the space.

Thus, the atmosphere acts as a green house, trapping the heat. Man can survive on earth only because of this green house effect. The gases in the atmosphere most responsible for keeping the earth’s surface warm are carbondioxide (CO₂), nitrous oxide (N₂O) and water vapours. These gases are called as green house gases. CO₂ CH₄, CFCs and (N₂O) are also termed as radiatively active gases as they can absorb long wave infrared radiation.

Man is adding large amount of CO₂ to the atmosphere each year by burning fossil fuels in homes, industries and automobiles, biomass burning associated with agricultural practices etc. Methane is added to the atmosphere by marshes, paddy fields, cattle sheds and biogas plants. Chlorofluorocarbons are emitted by refrigerators and air conditioners.

Nitrogen oxides are produced from organic matter and fertilizers by denitrifying bacteria as well as from automobiles exhausts and industries. Recently, the concentrations of these green house gases in the atmosphere have increased and this is affecting the global climate. The increase in mean global temperature due to increased concentrations of greenhouse gases is called global warming.

Global Warming:

Definition : Global warming refers to a gradual rise of temperature in the atmosphere and the consequent change in the global radiation balance mainly due to anthropogenic processes leading to climatic change at different levels-local, regional and global.

Causes : About 75% of the solar energy reaching the Earth is absorbed by the Earth’s surface, which increases its temperature. The rest of the heat radiates back to the atmosphere. Some of the heat is trapped by greenhouse gases [GHGs], mostly carbon dioxide. As carbon dioxide is released by various human activities, it is rapidly increasing. This causing global warming.

According to the Director of the Philippines Atmospheric Geophysical and Astronomical Services Administration [PAG-ASA], global warming and consequent temperature rise can be mostly attributed to the developed countries which heavily depend on automobiles, air-conditioning and other high-tech amenities which produce CO and methane.

Carbon dioxide contributes 60% of global warming and comes mostly from the burning of fossil fuels such as coal, oil and natural gas. Methane contributes 15-20% in global warming. It is derived from flooded paddy fields, livestocks, waste dumps and coal mining.

Effects of Global Warming :

• Global warming could cause climatic change, increasing in temperature, acid rain, increased rate of ultraviolet (UV) rays penetraion, increased ozone in the troposphere acting as the primary component of atmospheric smog.
• The effects on the biosphere include the loss of habitat, depletion of coral reserves, loss of biodiversity, forest fires, desertification and so on.
• 10-15% of the arable land and economic reproductivity of such areas could be lost.
• High concentration of carbon dioxide will have fertilizing effect and will encourage plant growth.
• Some animals may die due to intolerance of increased amount of heat.
• Insects would start breeding more vigorously.
• Food chains will be altered and breeding time of many species would be affected.
• Many wetlands would dry out.
• It would cause large scale migration of people living on the coastal areas due to inundation of coastal areas.

Remedies : The remedial measures have been summarized below :

a. Control of Carbon dioxide emission : A drastic cut in the fossil fuel consumption is needed, particularly in the developed countries of the world with almost 50% of the world consumption of fossil fuel.

b. Alternative energy : If the Toronto Resolutions (1988) demanding a drastic cut of 20% fossil fuel emission are to be implemented, more emphasis should be given on developing new alternative fossil fuels. Recently the use of CNG and liquefied petroleum gas [LPG] in a few metre of the world has proved successful. These substitutes cause very low pollution.

c. Others :

• Increasing the vegetation cover particularly forests for photosynthetic utilisation of CO₂.
• Replacing chlorofluorocarbons with substitutes having little effect on global warming and ozone.
• Minimizing the use of nitrogen fertilizer’s by relying more and more on nitrogen fixation.

Measures for Reducing Air Pollution:
Air pollution can be controlled or reduced by taking some measures. These measures are discussed in the next page :

1. Checking of Industrial Pollution : For checking industrial pollution it is necessary to remove particular matter and gaseous pollutants from the industrial wastes. The removal of particular matter is possible by using devices such as cyclone collectors which remove about 70% of the particles; electrostatic precipitators (ESPs) which can remove the particles from gas by applying electrical forces with in the precipitator’s chamber, and can effectively remove 99 per cent of the particulars.

2. Remove gaseous pollutants : In order to remove gaseaus pollutants, wet systems may be used these are washing towers in which the fluid of alkali circulates, and reacts with ‘sulphur dioxide’ to produce a precipitate. In wet-dry systems, calcium hydroxide and charcoal are used as pollutant absorbents in drycleaning plants, paint factories, breweries, food processing plants, pharmaceutical industries etc.

3. Enforcement of laws :The problems related to industrial pollution can be controlled by enforcing laws. For example, the recent supreme court judgement in India has forced all the industries in Mathura and Agra (surrounding the historic Taj Mahal) to either upgrade their machineries or shift to other places because industrial pollution was causing damage to the Taj Mahal’s structure.

For checking pollutant emission from vehicles, the following methods are adopted

• applying new proportion of air and gasoline.
• maintaining more exact time for feeding fuel,
• using gas additives for improvement of combustion.
• converting exhaust compounds of vehicles to less toxic materials by injecting air into the exhaust.
• updating engine design to eliminate poisonous gases like carbon monoxide (CO), nitric oxide and hydrocarbon productions.

4. Afforestation and check on deforestation: Clearing of forested area by felling the trees should be prohibited by law. Afforestation or planting trees should be encouraged. In India Forest Conservation Act was passed in 1980, which was ammended in 1988.

5. Mass awareness programme : Regular campaigning against air pollution through newspapers, radio, television can be quite effective for protection air pollution. The harmful effects of air pollution and the source and nature of different pollutants may be highlighted through all these awareness programmes. Taking up programmes like ‘Van Mahotsav’ (planting of new saplings). ‘Social forestry'(1990 growing trees for the benefit of’ people or farmer), ‘Agro-forestry’ (yields by combining food crops with tree crops at the same time).

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 7 Weather and Climate offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 7 Question Answer – Weather and Climate

Objective Type Questions [1 mark each]

Question 1.
What is the normal lapse rate of temperature?
Answer:
1°C for 165 metre.

Question 2.
Which rays are hotter-vertical or slanting ?
Answer:
Vertical

Question 3.
Name the condition when the temperature increases with height.
Answer:
Inversion of temperature

Question 4.
When is daily maximum temperature recorded?
Answer:
In the afternoon.

Question 5.
In which areas is daily range of temperature low?
Answer:

• coastal areas.
• clouded areas.

Question 6.
In which areas is daily range of temperature high?
Answer:

• In interiors of continents
• In deserts

Question 7.
What are isobars?
Answer:
Lines of equal pressure.

Question 8.
What change takes place in the process of evaporation?
Answer:
Water is changed to water vapour.

Question 9.
What is condensation?
Answer:
Cooling of saturated air.

Question 10.
At what temperature, does condensation take place ?
Answer:
At dew point.

Question 11.
What is the percentage of humidity at dew point?
Answer:
100 per cent.

Question 12.
State the different forms of condensation.
Answer:
Frost, snow, dew, fog, mist, and clouds.

Question 13.
In which unit, is relative humidity measured?
Answer:
In percentage.

Question 14.
What is the relation between relative humidity and rainfall?
Answer:
When relative humidity is 100 per cent, rainfall takes place.

Question 15.
Name the different forms of precipitation.
Answer:
Rain, snow, hailstone.

Question 16.
What is the general cause of rainfall?
Answer:
Cooling of saturated air.

Question 17.
Which instrument is used to measure mean daily temperature?
Answer:
Maximum and Minimum Thermometer.

Question 18.
Who invented Maximum and Minimum Thermometer?
Answer:
J.Six.

Question 19.
Which instrument is used to measure atmospheric pressure ?
Answer:
Barometer.

Question 20.
Name the instrument used to measure relative humidity.
Answer:
Wet and Dry bulb thermometer.

Define the following briefly : 2 marks each

Question 1.
Insolation.
Answer:
Insolation means the incoming solar radiation on the earth’s surface.

Question 2.
Conduction.
Answer:
It is the process of transfer of heat through contact.

Question 3.
Inversion of Temperature. ar
Answer:
It is the condition when the temperature increases with height.

Question 4.
Isotherms.
Answer:
Isotherms are the lines joining the places of equal temperature reduced to sea level.

Question 5.
Atmospheric Pressure.
Answer:
It is the weight of a column of air extending from the ground to the uppermost layer of the atmosphere.

Question 6.
Millibar.
Answer:
One millibar is equal to force of one gram per sQuestion cm or a force euqal to 1000 dyne per sq.cm.

Question 7.
Pressure gradient.
Answer:
It is the rate of which the horizontal pressure changes.

Question 8.
Humidity.
Answer:
Humidity means the amount of water vapour in air.

Question 9.
Absolute humidity.
Answer:
Absolute humidity is the weight of actual water vapour present per unit volume of air.

Question 10.
Relative humidity.
Answer:
Relative humidity is the ratio between the actual humidity of air and the maximum vapour capacity at a given temperature.

Comparison type questions: 3 marks each

Question 1.
Weather and Climate:
Answer:

Weather	Climate
1. Weather stands for actual atmospheric conditions for a short period.	1. Climate is composite pictures of atmospheric conditions for a longer period (30 years).
2. The weather changes from day-today.	2. The climate is everlasting and does not change often.
3. Weather is actually present at a place. It is what you get.	3. Climate is what you expect.
4. Weather refers to a particular place.	4. Climate refers to a particular area.
5. Weather is uncertain and we can only forecast it for a short time ahead.	5. Climate has a high degree of accuracy and it is similar year after year.

Question 2.
Condensation and Evaporation
Answer:

Condensation	Evaporation
1. Condensation is the process by which water vapour is changed to water.	1. Evaporation is the process by which water is changed to water vapour.
2. Cooling of air leads to condensation.	2. High temperatures favour evaporation.
3. This change takes place from gaseous to liquid condition.	3. This change takes place from liquid to gaseous condition.

Question 3.
Relative Humidity and Absolute Humidity
Answer:

Relative Humidity	Absolute Humidity
1. It is a ratio between the actual amount of water vapour present in an air at the temperature and the maximum amount of water vapour that the air can hold at the temperature.	1. The total amount of water vapour present in an air at a particular temperature is absolute humidity.
2. It is a ratio between the absolute humidity and vapour capacity of the air.	2. It is defined as weight of water vapour per unit volume of air.
3. It is maximum in equatorial region, but is lowest in hot deserts.	3. It is maximum over oceans and lowest in high pressure areas.

Question 4.
Dew and Dew Point
Answer:

Dew	Dew Point
1. The droplets of water deposited on rocks, grass, leaves and the ground are termed as dew.	1. The temperature at which an air becomes saturated is called dew point.
2. Air, near the ground is condensed to form drops.	2. Condensation of air begins at this temperature.
3. Frozen drops of dew are known as frost.	3. The relative humidity at dew point is 100 %

Question 5.
Fog and Mist
Answer:

Fog	Mist
1. Fog is condensed water vapour hanging in the air.	1. Thin fog is called mist.
2. The visibility is less than 200 metre.	2. Visibility is more than 200 metre.
3. Fog is formed due to cooling of air on dust particles.	3. Mist is formed due to cooling of wet air by radiation.

Question 6.
Precipitation and Rainfall
Answer:

Precipitation	Rainfall
1. It is the collective name given to different forms of release of moisture afer condensation.	1. It is a type of precipitation when moisture falls on the earth in the form of droplets of water.
2. Precipitation has two forms : (a) liquid (b) solid.	2. When cloud particles grow heavy, they fall as rain drops (in liquid form).
3. Rainfall, snow, hail are the common forms of precipitation.	3. Three types of rainfall are convectional relief and frontal.

Answer the following questions briefly : 3 marks each

Question 1.
Define Temperature of a place.
Answer:
The Temperature means degree of hotness of a body. The temperature of a place means the temperature of the air at that place. It is measured in shade of the air upto the height of at least one metre.

Question 2.
What is Daily Mean Temperature?
Answer:
Daily Mean Temperature : The average of the maximum temperature and minimum temperature recorded during a day (24 hours) is known as daily mean temperature.

Daily Mean Temperature :

= \(\frac{\text { Max.Temp. }+ \text { Min.Temp. }}{2}\)

For example, if a place has the maximum temperature of 39° C and minimum temperature of 27° C for a particular day, the daily mean temperature

= \(\frac{39^{\circ}+27^{\circ}}{2}=\frac{66^{\circ}}{2}=33^{\circ} \mathrm{C} \text {. }\)

Question 3.
What do you mean by Monthly Mean Temperature?
Answer:
Monthly mean temperature
: The average of the daily mean temperature of all days of a month is known as monthly mean temperature.
Monthly Mean Temperature of July

= \(\frac{\text { Daily Mean Temp. of } 1+2+3 \ldots 31 \text { days }}{31}\)

Question 4.
Name the factors which affect the range of temperature of a place.
Answer:
(a) Latitude
(b) Distance from the sea
(c) Ocean currents
(d) Prevailing winds
(e) Soils
(f) Cloudiness.

Question 5.
What is inversion of Temperature?
Answer:
Inversion of Temperature : Under normal conditions the temperature decreases with increasing height at the rate of 1° C per 165 metre. This is known as ‘Normal Lapse Rate’. But sometimes, the conditions are reverse so that the temperature increases with height locally and temporarily. This condition in which the colder air nearer the earth and the warmer air above is called inversion of temperature.

Question 6.
What is Absolute Humidity?
Answer:
Absolute Humidity :
Definition: Absolute humidity refers to the total amount of water vapour present in a given volume of air. It is the weight of actual amount of water vapour present in a unit volume of air. According to D.S. Lal, The weight of water vapour per volume of air is referred to as the absolute humidity. Unit : The unit used to express absolute humidity is gram per cubic centimetre. For example, if the absolute humidity is 10 gm / cu cm. it means that in a sample of one cubic centimetre of air. the amount of water vapour present is 10 gm.

Question 7.
What is Relative Humidity?
Answer:
Relative Humidity : Definition: The ratio of the amount of water vapour present in the air mass at a given temperature of a place relative to the maximum quantity that could be present is called Relative Humidity. So Relative humidity is a ratio between the actual amount of water vapour present in the air and the maximum amount of water the air can hold at that temperature. Unit : Relative humidity is a ratio, but it is always expressed as a percentage.
Formula : Relative Humidity

Question 8.
What is Specific Humidity?
Answer:
Specific Humidity is defined as the mass of water vapour in gram contained in a kilogram of air and it represents the actual quantity of moisture in a definite air. According to H.J. Critchfield, Specific humidity is the ratio of the mass of water vapour actually in the air to a unit mass of air including the water vapour. Specific humidity is expressed as a gram/kilogram.

Question 9.
What do you mean by precipitation?
Answer:
Precipitation : Condensation of water vapour in the air in the form of water droplets and ice and their falling on the ground is collectively called Precipitation. It is a collective name given to various forms of moisture falling on the earth from condensation of water vapour in the atmosphere. In metereology, precipitation is defined as fall of water through the atmosphere to the earth’s surface in the forms of rainfall including drizzle, snowfall, sleet or hail.

Question 10.
Define rainfall ?
Answer:
Rainfall : Definition : When moisture-laden air rises up, condensation takes place and clouds are formed. If the clouds are further cooled, more condensation occurs and drops of water that are formed big in size. These big drops are too heavy to remain in the air and fall down towards the ground in liquid form. The falling of these drops of water from the clouds is known as rain. Rain drops are 0.5 mm to 6.35 mm in diameter.

Identify the correct answers :

Question 1.
About 35% of insolation returned to space is called
(a) Effective solar radiation
(b) Earth’s Albedo
(c) Heat balance
(d) Condensation
Answer:
(b) Earth’s Albedo

Question 2.
The lapse rate of temperature is
(a) 4.6° C
(b) 5.6° C
(c) 6.4° C
(d) 7.5° C
Answer:
(c) 6.4° C

Question 3.
The annual range of temperature is minimum in
(a) Equatorial region
(b) Tropical region
(c) Polar region
(d) Desert region
Answer:
(a) Equatorial region

Question 4.
Standard sea level air pressure is called
(a) 1013.2 mb
(b) 1014.2 mb
(c) 1015.0 mb
(d) 1016.0 mb
Answer:
(a) 1013.2 mb

Question 5.
An imaginary line on map joining places with same air pressure is called
(a) Isotherm
(b) Isohyte
(c) Isobar
(d) Isoplate
Answer:
(b) Isohyte

Question 6.
Closely located isobars denote
(a) High pressure
(b) Low pressure
(c) Medium pressure
(d) No pressure
Answer:
(b) Low pressure

Question 7.
The actual mass of water vapour in the air is called
(a) Relative humidity
(b) Absolute humidity
(c) Specific humidity
(d) Cloud
Answer:
(a) Relative humidity

Question 8.
The instrument used to measure humidity is
(a) Barometer
(b) Hygrometer
(c) Anemometer
(d) Thermometer
Answer:
(b) Hygrometer

Question 9.
The ratio of weight (in gram) of water vapour to the total weight (in kilogram) of moist air is expressed as
(a) Specific humidity
(b) Relative humidity
(c) Absolute humidity
(d) None of these
Answer:
(a) Specific humidity

Question 10.
The actual mass of water vapour per unit volume of air is known as
(a) Relative humidity
(b) Absolute humidity
(c) Specific humidity
(d) None of these
Answer:
(a) Relative humidity

Question 11.
Wind speed is measured by instrument
(a) Sextant
(b) Rain gauge
(c) Hygrometer
(d) Anemometer
Answer:
(d) Anemometer

Question 12.
Energy is released when water vapour
(a) precipitates
(b) condenses
(c) evaporates
(d) rains
Answer:
(b) condenses

Question 13.
The temperature varies primarily according to latitude mainly because
(a) the earth is a large planet
(b) the earth rotates on its axis
(c) the earth is spherical in shape
(d) the earth is far away from the sun
Answer:
(c) the earth is spherical in shape

Question 14.
Normal lapse rate of the atmosphere is 1° for every
(a) 132
(b) 165
(c) 185
(d) 225
Answer:
(b) 165

Fill in the blanks with correct words : 1 mark each

1. _____ is the weight of air on 1 sQuestion cm. surface at sea level.
Answer:
1.3 kg

2. _____ millibars is the normal pressure of air.
Answer:
1013.2

3. _____ are lines of equal pressure.
Answer:
Isobars

4. Speed of sunrays is _____ km per second.
Answer:
3 lakh

5. The incoming solar energy intercepted by the earth is defined as _____
Answer:
Insolation

6. The _____ gas absorbs some of the ultra-violet radiation of the sun.
Answer:
Ozone

7. Land gets heated through the process of _____.
Answer:
Conduction

8. Water surfaces get heated by the process of _____.
Answer:
Convection

9. The amount of rainfall depends on the _____ content of the air.
Answer:
moisture

10. Snow storms are called _____.
Answer:
blizzard

11. The _____ scale is used to show the strength of the wind.
Answer:
Beaufort.

If the sentence is true, write ‘T’ and if false write ‘F’ against the following : 1 mark each

1. The weather keeps changing from day to day and can even change within a few hours.
Answer:
True

2. The climate of a region is the average weather condition over a span of 30-40 years.
Answer:
True

3. 51% of the heat of sun that reaches the earth’s surface is almost entirely reflected back at night. This is known as Terrestrial Radiation.
Answer:
True

4. The difference between the highest and lowest temperature in a day at a place
is known as the annual range of temperature.
Answer:
False

5.Water starts boiling at 32° F or 0° C.
Answer:
False

6. Cloudy nights are usually hot and sultry.
Answer:
True

7. Temperature increases with increasing altitude.
Answer:
False

8.Temperature increases gradually from the Equator to the poles.
Answer:
False

9. The higher we go the heavier the air becomes.
Answer:
False

10. When the sky has 25 % of cloud cover we say it is almost cloudy. cover we say it is almost cloudy.
Answer:
False

Weather and Climate Class 6 WBBSE Notes

Weather : Weather is the sum total of atmospheric conditions at any place, at any specific time (a short period). The weather changes from day-to-day and hour-to-hour. The Indian Meteorological Department publishes the daily Indian weather maps.

Climate : Climate is the description of atmospheric conditions of an area over a long period (say 35 years). Thus climate is the average weathering of a place over a long period of time.

Elements of weather and climate: The elements of weather and climate are-

• Temperature
• latitude
• Altitude
• Distribution of land and water
• Pressure distribution
• Prevailing winds
• Ocean currents
• Mountain barriers.

Introduction :

Every now and then we talk about weather. When we discuss about the weather of a place, we talk about how hot or cold the day is, whether it is rainy, cloudy or sunny and the like. In this chapter we shall learn about weather and climate. Weather is the name given to the atmospheric conditions formed by changing atmospheric elements, like air temperature, air pressure, air humidity, rainfall/snowfall, winds, sunshine, cloudiness etc. of a particular place or a particular day or a part of a day. Weather is essentially a day-to-day or even an hour-to-hour phenomenon. Climate is a description of many different kinds of weather that are generally found at a given place over a long period of time.

Definition of weather : Weather refers to the sum of the atmospheric conditions at any place or in an area at a particular time. Weather is the description of the atmospheric conditions of a particular place at a particular time or a short period of time. Weather is essentially a day-to-day or even an hour-to-hour phenomenon.

Definition of climate: The average weather conditions and variations in these conditions over a long period of time such as a season or a year is termed as climate. The climatic data is based on calculated averages of data recorded over a period of 35 years.

Elements of Weather and Climate –

Difference between Weather and Climate –

Weather	Climate
1. It describes the atmospheric conditions for a short period of time.	1. It describes the atmospheric conditions over a long period of time.
2. Weather is essentially a day-today or even an hour-to-hour phenomenon.	2. Climate is generally a variation over a long period of time such as a season or a year.
3. The description covers a smaller area.	3. The description covers a larger area.
4. Weather data is obtained through direct observation or by the use of instruments.	4. Climate data is based on calculated averages of data recorded over a period of 30-35 years.
5. It refers to a particular place.	5. It refers to a particular region.

Major Elements of Weather and Climate

What do you mean by the term of ‘Elements of Weather and Climate’?

The atmospheric conditions, which make up the sum total of climate, are called elements of weather and climate. These elements vary from place to place and from time to time. All these elements comprise the following :

1. Air Temperature
2. Air Pressure and Wind
3. Cloudiness and Rainfall.

Air Temperature : Temperature is the amount of heat that a place receives and it is known by measuring the temperature of air of a place. The air and minute dust particles of air become hot by the rays of the sun. The warmth of the air is known as Air Temperature. The temperature of a particular place denotes the degree of hotness of air at that place. Thermometer is the instrument that measures air temperature. The sun is 150 million km away from the earth.

The sun is 1,00,000 times bigger than the earth. The surface temperature is estimated at 6000° C. The sun’s core has an estimated temperature of 14,000,000° C. The sun radiates energy in the form of electro-magnetic waves of short wavelength.

These waves travel in all directions from the sun. The earth, owing to its small size and great distance from the sun, intercepts only a small fraction of the energy \(\frac{1}{2000,000,000}\) radiated by the sun. The radiant energy received by the earth is called the incoming solar radiation or insolation. The incoming solar energy intercepted by the earth is defined is insolation.

According to H.C. Critchfield, “Radiant energy from the sun that strikes the earth is called isolation.” If we consider 100 % of insolation entering the earth’s atmosphere, nearly 35 % of the total insolation scattered and reflected by clouds (26%), dust particles molecules (7 %) and surface of the earth (2 %) (26 % + 7 % + 2 % = 35 %).

This loss of insolation is called Albedo (35%). The 35 % insolation is therefore, not used for heating the atmosphere. Remaining (100-35) % = 65 % of the incoming solar radiation takes part in warming up the atmosphere directly and indirectly and is called an Effective Solar Radiation. The atmosphere directly absorbs only 14 % of the incoming insolation. The rest (65-14) % or 51 % of incoming solar radiation is transmitted to the surface of the earth. This incoming solar radiation (insolation) first heats the solid and liquid surfaces and then the earth radiates back to the air in contact with it and atmosphere is gradually heated. These are called indirectly Effective Solar Radiation.

Processes of Heating of the Atmosphere : The air is heated by the following main processes :

Radiation : It is a process by which heat waves are sent out by the earth’s surface. At first, the surface of the earth is heated by the sun. The heat of the earth’s surface is then radiated to the lower atmosphere. The air in the lower layer of the atmosphere gets heated.

Conduction: A particle transmits heat to another particle in contact with it. This process is called conduction. The lower layers of air are heated by conduction of heat from the earth’s surface. The upper layers are heated by lower layers through conduction.

Convection : The air particles being heated by their contact with the earth’s surface become lighter and rise up. The comparatively cool air particles in the upper layers are heavier and come down slowly. In this way air currents are formed and these are known as convection currents.

Difference in Temperature between day and night :

Maximum Temperature: The highest temperature of the day is called Daily Maximum Temperature. The sun is the highest at noon but the highest temperature does not occur at 12.00 noon because the atmosphere receives heat from the earth’s surface slowly. The maximum temperature is attained by 2.00 p.m. after the noon. If we note the highest temperature of a month, it is called Monthly Maximum Temperature.

Minimum Temperature: The lowest temperature of a day is called the Daily Minimum Temperature. The Daily Minimum Temperature at a place does not occur at 12:00 midnight but at about 4:00 a.m. in the morning because radiation of heat continues up to the sunrise.

Daily or Diurnal Range of Temperature: The difference between the maximum and minimum temperatures recorded during a day is called Diurnal Range of Temperature. Daily range of temperature is minimum in equatorial region and maximum in tropical desert region.

Annual Range of Temperature: The difference between the mean temperature of the hottest month and that of the coolest month in a year is called the Annual Range of Temperature.

When the diurnal ‘range of temperature’ is high, days are usually very hot and nights are cold. High annual range of temperature makes the summers scorching hot and the winters very cold.

Measurement of Temperature:

Temperature is measured in degree celsius (centigrade scale) i.e. °C or Fahrenheit scale i.e. °F. Temperature of melting point of ice is taken as 0° C or 32° in Fahrenheit scale and the temperature at which water boils is taken as 100° C and there are 100 divisions. Following formula is used for inter conversion of temperature between Centigrade scale and Fahrenheit scale. °F = (°C × \(\frac{9}{5}\)) + 32.

Conversions : Celsius (°C)

= Fahrenheit -32° × \(\frac{5}{9}\) and Fahrenheit (°F) = (Celsius .× \(\frac{9}{5}\))+32°.

The temperature of air is always measured in the shade because in the open direct radiation from the sun will affect the reading. Low and moderate temperates usually up to 500° C is called thermometry. Temperatures above this range are called Pyrometry. Water freezes to ice at 32° Farhenheit (F) or 0° Centigrades (C). Water starts boiling at 212° F or 100° C.

Instrument for measuring temperature: The degree of heat of any body is measured by its temperature. A clinical thermometer is used to measure the temperature of our body. We can also use a thermometer for measuring atmospheric temperature. We can measure the highest and lowest temperatures in a day by a ‘Six’s Thermometer’.

Six’s Maximum and Minimum Thermometer : This thermometer is designed so as to record both the maximum (highest) and minimum (lowest) temperature experienced during a day. The instrument consists of a U-shaped glass tube with a long cylindrical bulb bent downwards at one end and a spherical bulb at the other end.

Factors affecting air temperature :

(a) Latitude : Due to the spherical shape of the earth the angle of incidence of sunrays is not the same everywhere on the surface of the earth. Direct rays of the sun produce more heat than the slanting rays.

The region near the Equator gets more direct rays of sun and are therefore, hot throughout the year. On the other hand, outside the tropics, the rays are spread over a larger area and pass through a longer distance. Therefore temperature gradually decreases from the Equator to the Poles.

(b) Altitude : The density of air decreases as you go higher and there are less impurities away from the surface of the Earth, the temperature decreases with the increase in height above sea level. Up to a certain height the temperature decreases at the rate of 1° C for 165 m height above the sea level. Or we may say, temperature decreases at the rate of 6.5° C per kilometer altitude. It is known as the normal lapse rate of temperature.

(c) Distance from the sea: Due to the phenomena of land and sea breezes the temperatures of the coastal margins is comparatively cooler than that of a place situated far away from the sea.

Inversion of Temperature :

Under normal condition, temperature decreases at the rate of 6.5°C per 1000 metre. But sometimes, the conditions show the reverse of the normal situation. So that temperature increase with height, locality and temporarily. This condition in which the cooler air is nearer on the earth’s surface and the warmer air above on it is called inversion of temperature. It generally occurs in mountain valleys, especially in winter on calm clear nights.

(d) Length of Day and Night: Summer days are longer than winter days. Longer periods of daylight heat the earth more. So summer temperature is higher than winter temperature.

(e) Cloud : Clouds check solar radiation. Absence of clouds make a day very hot and a night very cold.

Temperature Belts of the World –

We can divide the globe into 5 temperature belts on the basis of variation in temperature from the equator towards the poles:

1. The Torrid belt
2. The North Temperate belt
3. The South Temperate belt
4. The North Frigid belt
5. The South Frigid belt.

(i) The Torrid belt : This belt extends between the Tropic of Cancer (23 \(\frac{1}{2}\)° N) and the Tropic Capricorn (23 \(\frac{1}{2}\)° S). This is the hottest part of the earth with mean temperature above 20° C. The sun shines over this belt more or less vertically throughout the year.

(ii) & (iii) The North and South Temperate belts : Temperate belt extends between 23 \(\frac{1}{2}\)° and 66 \(\frac{1}{2}\)° latitudes in both the hemispheres. This is the belt of moderate temperature (between 10° to 20° C ).

The summers are not very hot, and the winters are not very cold. The temperate zones of both the hemispheres can be divided into two parts: (a) warm temperate-zone between 23 \(\frac{1}{2}\)° and 50° latitudes and (b) cool temperate zone between 50° and 66 \(\frac{1}{2}\)° latitudes.

(iv) & (v) North and South Frigid belts : Frigid zones extends between 66 \frac{1{2 and the Pole in both the hemispheres. Temperature is constantly low throughout the year because of slanting rays of the sun. These are the coldest parts of the earth with mean temperature below 10° C. The land remains frozen almost throughout the year.

Isotherms : Definition : Isotherms are imaginary lines drawn on a map joining places of the same average temperature for a specified period, supposing them to be at sea level (reduced to sea level).

Characteristics : (i) Isotherms bend to east-west, generally following the latitudes, (ii) The July isotherms bend towards equator over the oceans and polewards on land, (iii) The January isotherms bend just reverse of it, (iv) Isotherms take sudden bends where land-water contrasts are maximum, (v) The spacing of isotherms indicates latitudinal thermal gradient i.e. steepness or slow gradual nature of temperature change.

Humidity : The amount of water vapour present in the air varies from place to place and from time to time at the same place. The amount of water vapour present in the atmosphere is referred to as humidity. Humidity of the atmosphere is high when it has large quantities of water vapour. The water content of the atmosphere is indicated by Absolute Humidity. Relative humidity is a more useful measure of humidity of the atmosphere than absolute humidity.

The water vapour holding capacity of the air is related to its temperature. Hot air can hold more water vapour than cold air. Relative humidity is the ratio between the quantity of water vapour present in the atmosphere at a given temperature to the maximum quantity of water vapour that the atmosphere can hold at that temperature. Relative humidity is expressed in percentage. Relative humidity is high in the equatorial regions and is the minimum in the tropical deserts.

When the relative humidity of air is 100 %, the air is said to be saturated. The temperature at which air gets saturated is called the dew point. Humidity of air is measured by hygrometer.

Saturated air : Air is said to be saturated when it contains water vapour in its full capacity. The temperature at which the air is saturated and below which condensation (the transformation of water vapour into water or ice) begins is called the dew point.

Determination of humidity : Humidity is measured by an instrument named Hygrometer which comprises wet and dry bulb thermometers [Fig-7.8]. Atmospheric humidity is expressed in a number of ways – absolute humidity, relative humidity and specific humidity.

The actual amount of water vapour present in the air at a particular temperature is called the absolute humidity. It is expressed in gram per cubic centimetre of air. Relative humidity is defined as the ratio of the amount of water vapour in the air to the amount the air can hold at that temperature. Relative humidity is generally expressed in percentage. For example, if the humidity capacity and absolute humidity of air having temperature of 20° C are 8 grams and 4 grams per cubic centimeter respectively, the relative humidity will be as follows :

Specific humidity is defined as the mass of water vapour in grams contained in a kilogram of air and it represents the actual quantity of moisture in a definite air.

Role of humidity in the atmosphere :

1. The atmospheric humidity is of vital climatic importance because different forms of precipitation, storms and turbulence etc. depend on humidity.
2. Human comfort depends considerably on the humidity of the atmosphere especially in hot countries. High relative humidity means discomfort and low humidity causes skin to become rough and cracked.
3. Relative humidity determines the rate and amount of evaporation. So it is an important climatic factor.
4. Water vapour absorbs terrestrial radiation and thus helps in heating the earth’s surface and the lower atmosphere.
5. Through the condensation of water vapour, huge amount of energy is released into the atmosphere in the form of latent heat of condensation, driving force for most of the storms.

Air Pressure and Wind : The atmosphere surrounding the earth exerts pressure on the earth’s surface owing to its weight. We do not feel the effect of this pressure because we are accustomed to it from our birth.

Definition of air pressure : Atmospheric pressure is the pressure at any point on the surface of the earth due to the weight of the column of air above that point. Thus air pressure, considering total weight of various layers of air in atmosphere, is maximum at sea level or on the surface of the earth.

Importance of air pressure : Air pressure is important for the following reasons :

1. It creates winds
2. It influences weather
3. Changes in air pressure give important clues in forecasting weather.

Units used to express atmospheric pressure:

Atmospheric pressure is not the same at all places at sea level. Pressure varies from place to place according to changes in temperature. At sea level, when the temperature increases, the atmospheric pressure decreases. The mercury barometer is the standard instrument for measuring atmospheric pressure. Pressure is read in centimetres or inches of mercury, a true measure of the height of the mercury column. Standard sea level pressure is 76 cm or 29.92 inches on this scale. Atmospheric pressure is measured with an instrument called ‘Barometer’.

Another pressure unit is used by meteorologists in drawing weather charts. At the earth’s surface the average air pressure is 1.03 kg. per sq. cm. This pressure is expressed in millimetres (mm) of mercury or millibar’si’ (mb). One bar is divided into 1000 milibars. Millibars are now known as hectopascals. One atmospheric pressure (76 cm of mercury) is equal to 1013 m b. The term ‘high pressuri denotes the state of the atmosphere when the barometer reads about 76 cm(1013 mb) or more. The term ‘low pressure’ denotes the state of the atmosphere when the barometer reads about 74 cm(986 mb) or less. At sea level, the barometer rarely falls below 71 cm(946 mb) or rises above 79 cm(1050 mb).

Isobars: The pressure of air is shown on weather maps by means of lines known as isobars, meaning ‘equal weight’. An isobar is an imaginary line drawn on a map (or a weather chart) joining all places with equal atmospheric pressure.

Factor affecting atmospheric pressure
The atmospheric pressure varies from place to place, region to region and from time to time due to the following factors :
i. Temperature : Air pressure has an inverse relation with temperature. The higher the temperature, the lower is the pressure. As air is heated, it expands and rises upwards. It becomes less dense and exerts less pressure. Conversely, cold air contracts; it becomes heavier and descends. This descending cold air exerts high pressure. Higher temperature is, therefore, associated with low pressure, an upward current of air and inflowing winds. On the other hand lower temperature is associated with high pressure, a downward current of air and outflowing winds.

ii. Altitude : Altitude variation causes variations in air pressure. The lower layers of air are denser than the upper layers. Moreover, the lower layers are compressed under the weight of the upper layers of air and that is why the lower layer exerts high pressure. As we go higher up, the atmospheric pressure decreases. Air pressure decreases at the rate of 10 mm per 110 metres rise in altitude.

iii. Water vapour : Air containing water vapour is lighter than dry air. The more the water vapour the lighter the air is. The humid air contains comparatively less nitrogen and oxygen but the dry air contains more of those. This makes the humid air lighter than the dry air. For this reason land winds are heavier than sea winds which are laden with water vapour.

iv. Rotation of the earth : The rotation of the earth and the centrifugal force resulting in swing of air in different areas, exerts some influence on air pressure. The sub-polar low pressure belts between 60° and 65° north and south are due to the rotation of the earth.

v. Distribution of land and water : Pressure conditions on land and water on the same latitude are not the same. During summer, the land gets heated more than the water, thus a low pressure region is created on the land compared to water. The opposite condition occurs during winter.

Mechanism and Types of Winds –

Definition : A current of air moving with any speed in horizontal direction is called wind while it is moving upwards and downwards, it is called air current. So air that moves parallel to the surface of the earth is known as wind and vertical movement of air is called air current. Wind is intimately related to pressure.

Wind Direction : A wind is named according to their direction from which it blows. For example, an easterly wind is one which comes from the east, westerly wind comes from the west and a north wind comes from the north.

Wind Speed : The difference of pressure between any two places is called pressure gradient or barometric slope. There is close relationship between pressure gradient and air circulation. The wind blows from areas of high pressure to areas of low pressure. It may be mentioned that the direction of pressure gradient is always from high pressure to low pressure. So air movement follows the barometric slope. When the barometer slope is steep, wind blows rapidly; when it is weak, wind becomes weak.

Measurement of Wind Direction : Wind direction is easily determined by an instrument named windvane or weather cock.
Measurement of Wind Speed : To measure wind speed, an instrument called the anemometer is used.
Unity of Wind Speed : The unit used to measure the wind speed or velocity is Knot (metre/mile per hour ; 1 Knot = 1,877 km / hours).

Beaufort Scale : Before adoptation of the instrument anemometer in early 1950s, Beaufort Scale was widely used for the measurement of the velocity of wind. This scale of wind strength was devised by Sir Francis Beaufort of the British Navy in 1805 to help sailors at sea. It was originally based on the effect of wind speed on a sailing ship. The scale is still in use today. There are 13 levels of wind strength ( 0 to 12) on this scale, ranging from dead calm to hurricane.

Clouds and Rainfall –

Definition of clouds : Clouds are formed when condensation occurs at altitudes far above the ground. Clouds consist of million of tiny water droplets and ice particles. Clouds are formed owing to the ascent of warm moist air. The cloud droplets are so tiny that they remain in suspension and do not drop on the ground. Clouds move about in response to winds and air currents and take on different shapes and sizes.

The measurable proportion of cloud in the sky is called ‘cloud cover’ or ‘cloudiness’.

When the air near the earth rises into the sky, it cools and some of its water vapour condenses into tiny droplets of water. This happens when the temperature of air is below the dew-point.

Condensation : Condensation is the process by which water vapour is converted into water. Condensation can only occur when the air becomes saturated. Air becomes saturated in two ways-

(i) By cooling of air : When the temperature of air decreases, its capacity to hold water decreases. The air becomes saturated with the same quantity of water vapour by a fall in temperature.
(ii) By the addition of more water vapour : When more evaporation occurs, the air becomes saturated. In nature, saturation of air in this manner is not a very common occurrence.

Precipitation: The process through which water from the atmosphere falls down on the earth is called precipitation.

Rain : Precipitation that reaches the ground in the form liquid is called rain. Rain drops are 0.5 mm to 6.35 mm in diameter.

Temperature and rainfall are the two most important elements of climate. Climate = temperature + rainfall. Precipitation which takes

place where the atmospheric temperature is below 0° C is called snowfall. The lightest form of precipitation is drizzle, which occurs in fine drops falling close together. Snow is precipitation composed of ice crystals. Sleet is a mixture of rain and snow. The rain gauge is the instrument to measure rainfall.

Elements of weather Measuring Instruments	Forms of Precipitation
1. Air temperature-Thermometer	1. Rain : Precipitation that reaches the ground in liquid form.
2. Atmospheric pressure-Barometer	2. Drizzle : Less intense rain.
3. Humidity of air-Hygrometer	3. Snow : Powdery mass of ice crystals.
4. Rainfall-Rain gauge	4. Sleet: Mixture of rain and ice.
5. Wind speed-Anemometer	5. Hail : Pellets of ice, associated with thunderstorms.

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 9 Noise Pollution offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 9 Question Answer – Noise Pollution

Answer the following questions briefly: (2 mark each)

Question 1.
Decibel.
Answer:
The unit to measure the intensity of sound is called decibel. It is measured by the instrument named decibel meter.

Question 2.
Write any one cause of noise pollution.
Answer:
The landing and taking off of aeroplanes can cause serious noise pollution to the residential complexes located at the vicinity of aerodromes.

Question 3.
Write any two measures for controlling noise pollution.
Answer:

• Playing of loudspeakers, bursting of crackers should be restricted to a bearable limit.
• ‘Silence board’ should be hung near hospitals, schools, libraries etc. in order to restrict people from making noise in those areas.

Question 4.
Define noise pollution.
Answer:
When sound turns intolerable, painful and irritable to people, it produces sound pollution.

Question 5.
Write any two harmful effects of noise pollution.
Answer:

• The capability to hear can get reduced gradually as a result of noise pollution.
• Noise pollution can cause high blood pressure, insomnia, heart disease, eye ailments, nerve disorders, gastric and digestive problem.

Identify the correct answers (MCQ): (1 mark each)

Question 1.
Decibel is a …………..
a. musical note
b. musical instrument
c. a measure of sound level
d. none of these
Answer:
c. a measure of sound level

Question 2.
It is physically and mentally uneasy if the sound crosses the limit of ………….
a. 20 dB
b. 40 dB
c. 65 dB
d. 70 dB
Answer:
c. 65 dB

Question 3.
The instrument to measure the intensity of sound is ………….
a. hygrometer
b. decibel meter
c. Anemometer
d. Six’s Thermometer
Answer:
b. decibel meter

Question 4.
Natural source of noise pollution is ………….
a. volcanic eruption
b. bursting of crackers
c. loudspeakers
d. screaching of tyres.
Answer:
a. volcanic eruption

Fill in the blanks with the correct words: (1 mark each)

1. The influence of noise pollution is far greater on _____ folk compared to rural ones.
Answer: urban

2. The rate of illness related to noise pollution is more among _____ people.
Answer: urban

3. It is legally forbidden to blow _____ near school, hospitals.
Answer: horn

4. Exposure to prolonged, high volume and monotonous _____can bring irritation, tiredness and pain.
Answer: sound

5. _____ pollution can cause high blood pressure.
Answer: Noise

If the sentence is true, write ‘T’ and if false write ‘F’ against the following. (1 mark each)

1. The unit to measure the air pollution is called decibel.
Answer: False

2. When sound turns intolerable, painful and irritable to men, it produces sound pollution.
Answer: True

3. Volcanic eruption with sound is an example of man-made noise pollution.
Answer: False

4. Noise pollution is comparatively less in villages.
Answer: True

5. Intensity of sound of vehicles on a busy road is 70 dB
Answer: True

Match the Following (1 mark each)

Sound	Intensity (dB)
1. Loudspeaker	a. 300
2. Siren	b. 100
3. General talk	c. 90
4. Loud music	d. 65
5. Jet plane	e. 80

Answer:

Sound	Intensity (dB)
1. Loudspeaker	e. 80
2. Siren	a. 300
3. General talk	d. 65
4. Loud music	c. 90
5. Jet plane	b. 100

Noise Pollution Class 6 WBBSE Notes

Chapter at a Glance

Pollution : Pollution occurs when something is added to the environment which is harmful or poisonous to people, animals and other living beings.

Noise Pollution : The harmful noise in the environment, such as the sound of cars and buses and trucks in a city or a village, loud speakers, etc. is called noise Pollution. Noise pollution can be defined as the unwanted sound in the atmosphere.

Effects (on Human health) :

• Hearing Problems : Any unwanted sound that our ears have not been built to filter in, can cause problems within the body.
• Sleeping Disorders : Loud noise can certainly hamper our sleeping pattern and may lead to irritation and uncomfortable situations.
• Health Issues : Excessive noise pollution in working areas such as offices, construction sites, and even in our homes can influence psychological health.
• Cardiovascular issues : Blood Pressure levels, cardio-vascular disease and stress related heart problems are on the rise.
• Trouble communicating : High decibel noise can put trouble and may not allow two people to communicate freely.

Introduction

Noise which can be described as an unwanted, untimely, unpleasant ‘voice’ is a pollutant that causes auditory illness [deafness] and non-auditory illness [psychosomatic disorders] over a long period of time. Any sound that causes pain and annoyance is regarded as noise and can be considered as one of the sources of pollution.

Definition of Noise Pollution : Unwanted or unpleasant sound that produces discomfort to humans and causes health hazards could be termed as Noise Pollution. Hence, the disturbing or excessive noise that can harm our activities or damage the balance of human or animal life can be said to be ‘noise pollution’.

Sources of Noise Pollution : High decibel (dB) noise is generated mainly from man-made sources such as horns, sirens, lawnmowers, television, mike, radio, loudspeakers, washing machines, food mixers etc.

Unit of Sound Measurement : Noise is measured by decibel (dB) unit. Noise levels up to 85 decibels are considered safe, but the limit is for eight hours a day, five days a week. Now, if the limit is exceeded even by 3 decibels, it causes damage to the hearing organ. The unit to measure the intensity of sound is called decibel (dB). It is measured by the instrument named decibel meter.

Noisiest Cities in India: In a country like India, and especially in a city like Delhi, people seem to have become inured to high levels of noise and do not foresee the imminent danger. Among the Asian countries, for instance, India has the highest level of noise pollution touching 80-90 decibels, with Delhi, Mumbai and Kolkata being the noisiest cities.

Noise Pollution and its measurement of intensity : The effects of noise pollution can be divided into auditory effects and non-auditory effects. Auditory effects encompass fatigue and deafness.

Non-auditory effects can be understood by a noise of 50 to 60 (dB) interfering with speech.

The Intensity of Different Sounds:

Causes of Noise Pollution:

Outdoor noise can be caused in the following ways especially in the urban areas.

• Poor urban planning : Poor urban planning may give rise to noise pollution.
• Residential and industrial noise pollution : Residential and industrial buildings situated side by side can result in noise pollution in residential areas.
• Noise pollution by sound system and festivals: Loudspeakers, musical bands, festivals and bursting of crackers at different public functions or during festivals disturb the peace and quietness of the environment.
• Noise pollution in cities from different sources : People in cities are exposed to constant blaring of horns, screeching of tyres as buses, trucks, lorries, motor cars and other fast moving vehicles try to overtake each other during busy hours.
• Sound of Aeroplanes : The landing and take-off of aeroplanes can cause serious noise pollution to the residential complexes located at the vicinity of aerodromes.

Others :

• Building of skyscrapers to accommodate the growing population is a common feature in the cities.
• At the construction sites of the multistoreyed buildings, noise produced by different machines and construction tools pose a serious problem in the neighbouring areas.

Silence Board : You must have noticed the ‘silence board’ hung near schools, hospitals and other institutions. This means that it is legally forbidden to blow horns near these institutions.

Intensity of different sounds : Noise about 85-90 decibels are considered to be dangerous. The WHO (World Health Organisation) has recommended a tolerance limit of 45 decibles for noise level at night and 55 decibles for day time.

Intensity and category of sounds and their effects : The effects of noise pollution can be divided into auditory effects and non-auditory effects. Auditory effects encompass fatigue and deafness. Non-auditory effects can be understood by a noise of 50 to 60 dB interfering with speech. Even low level of sound of considerable duration causes annoyance, high blood pressure, nausea, fatigue, anxiety etc. All these lead to a loss of working efficiency.

Others :

• Building of skyscrapers to accommodate the growing population is a common feature in the cities.
• At the construction sites of the multistoreyed buildings, noise produced by different machines and construction tools poses a serious problem in the neighbouring areas.

Silence Board : You must have noticed the ‘silence board’ hung near schools, hospitals and other institutions. This means that it is legally forbidden to blow horns near these institutions.

Intensity of different sounds : Noise about 85-90 decibels are considered to be dangerous. The WHO (World Health Organisation) has recommended a tolerance limit of 45 decibles for noise level at night and 55 decibles for day time.

Intensity and category of sounds and their effects : The effects of noise pollution can be divided into auditory effects and non-auditory effects. Auditory effects encompass fatigue and deafness. Non-auditory effects can be understood by a noise of 50 to 60 dB interfering with speech. Even low level of sound of considerable duration causes annoyance, high blood pressure, nausea, fatigue, anxiety etc. All these lead to a loss of working efficiency.

Noise pollution can be abated if we take the following measures:

• Implementation of laws can control the menace of noise pollution.
• Industrial location should be away from the residential areas. To do this, proper settlement planning is necessary.
• Silencing devices in noise-producing engines such as engines of aircrafts, automobiles, machineries in factories and home appliances could help. It is, at times, very difficult to eliminate high noise level in the case of factories. So, those factories can be set up in remote areas.
• High level of noise can be reduced by covering the room walls with acoustic tiles which act as sound absorbs.
• Persons, especially the workers employed in noise-prone areas, should be given protective devices such as ear plugs and ear muffs.
• Since natural vegetation has a tremendous ability to absorb and dissipate sound energy, trees should be planned along highways and in industrial areas to reduce noise.
• Playing of loudspeakers, bursting of crackers should be restricted to a bearable limit.
• ‘Silence board’ should be hung near hospitals, schools, libraries etc. in order to restrict people from making noise in those areas.
• The old noisy machineries should be replaced by new ones.
• Blowing hom should be prohibited in front of hospitals, near schools, libraries and official buildings.

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 6 Antarctica: The Ice-capped Continent offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 6 Question Answer – Antarctica: The Ice-capped Continent

Objective Type Questions [1 mark each]

Question 1.
What is the summer temperature range in Antarctica?
Answer:
-28° C and -38° C.

Question 2.
Which plants grow in the coastal areas of Antarctica ?
Answer:
During summer when some ice melts, mosses, fungi and lichens grow in the coastal areas.

Question 3.
What type of topography is found in most part of Antarctica?
Answer:
Most part of Antarctica is mountainous.

Question 4.
What are large mammals of the Antarctic Ocean ?
Answer:
Seal and whale are large mammals of the Antarctic Ocean.

Question 5.
When was Antarctica first discovered?
Answer:
In 1820.

Question 6.
Write the name of the largest research station in Antarctica.
Answer:
The Mc Murdo station established by USA is the largest research station.

Question 7.
What is the red, green and blue streaks of light in the sky of Antarctica called?
Answer:
Aurora Australis.

Question 8.
When was the Antarctic Treaty signed?
Answer:
In 1959 by 12 countries.

Give reasons for the following [2 marks each]

Question 1.
Antactica is known as the white continent.
Answer:
Antarctica is located around the south pole. It is completely frozen and is therefore known as the white continent.

Question 2.
There is great difference between the temperature in the coastal areas and at the centre of the ice-cap.
Answer:
Temperature ranges between -40° C and -75° C. Summer temperature on the coastal parts seldom rises above freezing point. In the interior parts the temperature remains between -28° C and 38° C

Question 3.
Antarctica is a cold desert.
Answer:
Antarctica is a cold desert with annual precipitation of 200 ~mm along the coast and far less within inland.

Question 4.
None of Antarctica’s mineral resources have been developed.
Answer:
Most of Antarctica’s minerals occur in amount too small to be mined profitably. Antarctica has deposits of coal, iron and copper. Petroleum may be present in the sea bed. None of Antarctica’s mineral resources have been developed.

Identify the correct answers : [1 mark each]

Question 1.
The white continent refers to
(a) Australia
(b) Europe
(c) Antarctica
(d) Asia
Answer:
(c) Antarctica

Question 2.
The Greek word ‘Antarktika’ means
(a) in the north
(b) in the south
(c) the opposite to north
(d)the opposite to south
Answer:
(c) the opposite to north

Question 3.
Antarctica lies closest to
(a) Australia
(b) Argentina
(c) South Africa
(d) New Zealand
Answer:
(a) Australia

Question 4.
The sun never sets in Antarctica during the month of
(a) January
(b) July
(c) June
(d) September
Answer:
(a) January

Question 5.
Antarctica is surrounded by the
(a) Arctic circle (66 1/2° N)
(b) Antarctic circle (66 1/2° S)
(c) Great circle (0°)
(d) Semi half circle
Answer:
(b) Antarctic circle (66 1/2° S)

Question 6.
The size of Antarctica ranks
(a) first
(b) second
(c) third
(d) fifth
Answer:
(d) fifth

Question 7.
The first man who visited the south pole was
(a) Captain Scott
(b) Roald Amundsen
(c) Columbus
(d) Captain Cook
Answer:
(b) Roald Amundsen

Question 8.
Indian first team to first touch Antarctica was in
(a) 1912
(b) 1952
(c) 1972
(d) 1982
Answer:
(d) 1982

Question 9.
Name of the ship of first Indian team to Antarctica was
(a) Indian ship
(b) Polar circle
(c) Gangotri
(d) Maitri
Answer:
(b) Polar circle

Question 10.
Antarctica was first discovered in
(a) 1732
(b) 1820
(c) 1922
(d) 1982
Answer:
(b) 1820

Fill in the blanks with correct words : [1 mark each]

1. Antarctica lies entirely in the ____ Hemisphere.
Answer:
Southern

2. ____ is an active volcano on the shores of the Rossa sea.
Answer:
Mount Erebus

3. Antarctica has ____ climate.
Answer:
Harsh

4. The seas around Antarctica have large swarms of small fish called ____.
Answer:
Krill

5. Floating and slowly moving blocks of ice are called ____.
Answer:
Ice berg

6. An Indian exped to Antarctica was first sent in ____.
Answer:
December, 1982

7. Permanent manned Indian research station called ____ and was set up in the year ____ .
Answer:
Maitri, 1990

8. ____ is being called a ‘Continent for Science’.
Answer:
Antarctica

9. The USA has taken the lead by establishing a minicity named ____ in Antarctica.
Answer:
MC Murdo

10. May to ____ is the winter season when there is no sun.
Answer:
July

11. ____ is a virgin continent.
Answer:
Antarctica

12. The ____ mountains are situated between lesser Antarctica and Greater Antarctica.
Answer:
Transantarctic

If the sentence is true, write ‘ T ‘ and if false write ‘ F ‘ against the following [1 mark each]

1. 99 % of the continent of Antarctica remains permanently covered with ice.
Answer:
True

2. Vinson Massif is the highest peak in Antarctica.
Answer:
True

3. The lowest recorded temperature is -90° C at Vostok station, on July 21, 1983.
Answer:
True

4. The Antarctica is the coldest desert.
Answer:
True

5. West Antarctica faces the Atlantic and Indian Ocean.
Answer:
False

6. East Antarctica borders the Pacific Ocean.
Answer:
False

7. Penguins of Antarctica are birds, but they cannot fly.
Answer:
True

8. Lambert Glacier is the longest glacier on earth.
Answer:
True

9. Penguins cannot fly, but they are good swimmers.
Answer:
True

Correct the following sentences : [1 mark each]

1. The vast permanent icy cover in Antarctica is known as the ice bergs.
Answer:
The vast permanent icy cover in Antarctica is known as Continental Ice Cap.

2. The strong and severe cold winds blow throughout the year. These are called drizzing.
Answer:
The strong and severe cold winds blow throughout the year, these are called the brizzards.

3. Actually, Antarctica is a national continent.
Answer:
Actually, Antarctica is an international continent.

4. The first man landing on Antarctica was Neil Armstrong.
Answer:
The first man landing on Antarctica was Roald Amundsen.

5. Antarctica is a continent dedicated to excavation.
Answer:
Antarctica is a continent dedicated to peace and science.

Antarctica: The Ice-capped Continent Class 6 WBBSE Notes

Location, shape and size : Antarctica is a fairly large continent. It stands fifth along the seven continents of the world. It lies entirely in the southern hemisphere having the south pole just in its centre. Unlike other continents, it keeps completely frozen all the year round with temperature never rising above 0° C. Evidently, the land is ever under a thick cover of ice. That is why this continent is called the white continent also.

Introduction :
A continent called Antarctica lies entirely in the southern hemisphere. It is a large continent of south polar region. This is the only continent which is completely frozen throughout the year. Therefore, it is called the ‘The white continent’. The vast permanent icy cover is known as the ‘continental ice cap’. We know very less about its relief and landforms because it is covered by the thick icy blanket. It is surrounded by large blocks of drifting ice called ‘ice bergs’.

Antarctica is the fifth largest continent of the world. It is surrounded by a vast, cold ocean called the Southern Ocean. This ocean is so cold that the surface-water temperature rarely rises above 4° celsius. It is because of the severe cold that this continent still remains uninhabited. No human beings can think of living here permanently.

Ancient Greek philosopher speculated that a landmass at the Earth’s southern end was needed to balance the land in the northern hemisphere. Such landmass was sighted in 1820 , proving the suppositions correct. This was named Antarctica. The Greek word ‘Antarktika’ means ‘the opposite to north’ or ‘opposite the bear.’ The bear is a constellation seen from the northernmost region of the Earth. It is the windiest, driest and iciest place on the Earth. Antarctica is larger than either Europe or Australia. It is about four times the size of India. This roughly circular continent is placed between the south pole and the 60° S parallel.

‘Antarctica’-The Ice-territory : Land and Boundaries : The total area of the continent is 14.2 million square km. in summer. During winter, Antarctica doubles in size because of the large amount of sea ice that forms along its periphery. About 99 % of the continent remains permanently covered with ice. In some places the thickness is up to 4800 metres. Underneath the ice, Antarctica has mountains, plains and valleys. The whole of this continent is a great plateau elevated to 2-5 km.

The Transantarctic mountains cross the entire continent. This mountains divide Antarctica into two parts-East Antarctica and West Antarctica.

1. East Antarctica : East Antarctica faces the Atlantic and Indian Ocean and covers more than half of the continent. Mountains, valleys and glaciers are found along the coast. A rift valley cuts into the coastline from the Indian Ocean. The central part is a plateau about 3000 metres above sea level. The eastern part of the continent is much wider than the western part. There are many glaciers in the continent. The Lambert glacier in East Antarctica is the world’s largest ice sheet. This glacier is about 100 km wide, over 400 km long and about 2500 m deep. Another glacier called the Beardmore glacier is one of the largest valley glaciers in the world having length of 201 km and width of 40 km.

2. West Antarctica : West Antarctica borders the Pacific Ocean. It

includes several mountain ranges and volcanoes. Most part of this region is mountainous. ‘Queen Maud Range’ divides mountainous part into two equal parts. Mount Erebus is an active volcano which is 3,795 metres high. It is permanently covered with thick ice. Mount Erebus is situated on the banks of Ross Bay off the Pacific Ocean. Vinson Massif (4897 m) is the highest peak of Antarctica. Vinson Massif is found in the Ellsworth Mountains near the peninsula.

The Antarctic Peninsula is a mountainous, S-shaped figure of land that points towards South America. The peninsula forms a continuation of the Andes Mountain chain of South America.

Climate : Antarctica is the coldest of all the continents. Icy winds make it even colder. The lowest recorded temperature is -90° C at Vostok station, on July 21, 1983.

1. Winter lasts from May to August. The average winter temperature is -70° C in the interior and -30° C at the coast.
2. December to February are the summer months. The average summer temperature is -35° C in the interior and 2° C at the coast.
3. There is a distinct difference between the summer and winter temperatures.
4. There is a great difference between the temperature in coastal areas and at the centre of the ice cap.
5. Most of the continent is dry. The interior receives an average of 5 cm of rain. The coastal areas are more moist. Annual coastal rain and snowfall average 60 cm. The Antarctica is a cold desert.
6. Winter from May to August is dark as Sun remains invisible. Streaks of blue, green, red etc. lights can be seen in the sky. The phenomenon is known as Aurora Australis.

Vegetation : Antarctica is a cold desert which cannot support normal and natural vegetation. A few plants grow in Antarctica because of the ice covered land and harsh climate. The most common plants are mosses and lichens. These plants cling to rocky areas, mostly along the coast. Some clumps of coarse grass and flowering plants are also found where the temperatures are milder.

Animal Life: The scanty vegetation is not enough to support animal life. Only a few insects and some tiny animals are found in Antarctica. The continent’s largest land animal is a type of fly not more than 2 cm long. There are penguins, seals and several sea birds which flock there during the summer season. Whales live in the surrounding sea. A small fish, called ‘Krill’ is found in plenty. The international laws are there for forbidding the killing of whales.

Discovery of Antarctica :

Antarctica was first discovered in 1820 but real exploration work began in

the 20 th century. Various countries claim the credit for the discovery of Antarctica. During the 19th century sailors sailed along its coast and found it was large enough to be called a continent.

Explorations began in the 20th century. The Norwegian explorer Roald Amundsen reached the south pole in 1911. In 1959, twelve countries signed a treaty to use the continent mainly for research.

Antarctica : The Continent of Science

This is the most inhospitable continent to man. Only scientists from different countries work here to find the solution of questions. This continent is not the territory of any country. It is an internationally owned landmass. Almost 40 countries have established more than 100 research centres here. These countries include the United States, Norway, Britain, Australia, New Zealand, Japan, France, Germany, Argentina and India. Scientists around the world are researching on the natural environment of Antarctica-its weather and climate, mineral resources, etc. This continent has got huge reserves of coal, petroleum, natural gas, copper, nickel and gold under its surface.

Indian Expeditions to Antarctica :

Indian scientific expedition to Antarctica was first sent in 1982. They started for Antarctica from Goa on December 1981. From 1982 to 1989 India sent about nine expeditions to this icy continent.

The first Indian team had 21 members. They were under the charge of Dr. S.Z. Qasim. As the journey was through roughest and most dangerous high seas, their ship named ‘Polar circle’ was equipped with two helicopters and two ice scooters. They set sail from Goa on December 6, 1981 and lastly they touched Antarctica on January 9,1982.

They stayed there for about ten days during which they carried out many experiments about climate, origin of the icy continent and its separation from the landmass etc. They set up a station there and named it ‘Dakshin Gangotri’. They discovered an undersea mountain on their way back and named it ‘Indira’. Facilities were erected between 1982 and 1985 at Dakshin Gangotri. Later on it was found that Dakshin Gangotri was drifting slowly because it was located on an ice shelf.

Second permanent manned station was located on a rocky foundation in 1990, called Maitri. It can accommodate 25 members. All the expeditions tried to know the possibilities of the existence of life and to solve the mysteries about the earth’s environment.

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 10 India: Our Motherland offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 10 Question Answer – India: Our Motherland

Objective Type Questions: (1 mark each)

Question 1.
How many islands are there in Andaman and Nicobar islands?
Answer:
204

Question 2.
What is the real source of strength of India?
Answer:
Unity in diversity

Question 3.
What is the total geographical area of India?
Answer:
32,87,263 sq. km

Question 4.
Between which latitudes and longitudes does the Indian subcontinent lie?
Answer:
Between 8°N to 37°N and 68°E to 97°E.

Question 5.
What is the east-west and north-south extent of India?
Answer:
East-west extent of India is 2933km. while the north south extent is 3214km.

Question 6.
How many states are coastal states?
Answer:
Nine states

Question 7.
How many islands are there in Lakshadweep islands?
Answer:
36

Question 8.
Name a group of coral islands.
Answer:
Lakshadweep

Question 9.
What is the name of Brahmaputra in Tibet?
Answer:
Tsang-Po

Question 10.
Which channel separates Andaman islands and Nicobar islands ?
Answer:
Ten degree channel

Question 11.
Name an active volcanic island in India.
Answer:
Barren island near Nicobar island

Question 12.
Which state is called “The Land of Dawn’?
Answer:
Arunachal Pradesh

Question 13.
Name one state in India where tropical evergreen forests are found.
Answer:
Kerala.

Question 14.
Name one region of India where thorn and scrub forests are found.
Answer:
Thar Desert.

Question 15.
Name three important trees found in tropical evergreen forests.
Answer:
Rosewood, Ebony, Gurjan.

Question 16.
Why are monsoon forests are called deciduous forests?
Answer:
Because these shed their leaves insummer.

Question 17.
Name three states where monsoon forests are found?
Answer:
Madhya Pradesh, Chhattisgarh and Jharkhand.

Question 18.
Name one important commercial tree of Madhya Pradesh.
Answer:
Teak.

Question 19.
Name three typical trees of coniferous forests.
Answer:
Pine, Deodar, Silver fir.

Question 20.
Name three important trees found in Tidal forests.
Answer:
Sundari, hogla, garan, gewa, gotpata etc.

Question 21.
Name the economically most important vegetation belt of India.
Answer:
Monsoon deciduous forests.

Question 22.
Name two typical trees
Answer:
Khair and Khajuri

Question 23.
Which state is the largest producer of wheat in India?
Answer:
Up

Question 24.
What is the harmful effect of too much rain on wheat crop.
Answer:
It cases mildew in wheat

Question 25.
Is rice is a kharif crop or a Rabi crop?
Answer:
Kharif crop

Question 26.
Which is the most important fibre crop in West Bengal.
Answer:
Jute

Question 27.
In which types of soils is coffee grown in India.
Answer:
Red soil and laterite soil

Question 28.
Which state in India produces the largest quantity of raw cotton?
Answer:
Gujarat

Question 29.
In which area was the coffee plantations started?
Answer:
Inchickmagalur

Question 30.
Name a disease of sugarcane ?
Answer:
Red Rot

Question 31.
Which is the main collecting centre for tea in southern India ?
Answer:
cochi

Question 32.
Which country is the native place of sugarcane?
Answer:
India

Question 33.
Name one state in India where tropical evergreen forests are found.
Answer:
Kerala.

Question 34.
Name one region of India where thorn and scrub forests are found.
Answer:
Thar Desert.

Question 35.
Name three important trees found in tropical evergreen forests.
Answer:
Rosewood, Ebony, Gurjan.

Question 36.
Why are monsoon forests are called deciduous forests?
Answer:
Because these shed their leaves in summer.

Question 37.
Name three states where monsoon forests are found?
Answer:
Madhya Pradesh, Chhattisgarh and Jharkhand.

Question 38.
Name one important commercial tree of Madhya Pradesh.
Answer:
Teak.

Question 39.
Name three typical trees of coniferous forests.
Answer:
Pine, Deodar, Silver fir.

Question 40.
Name three important trees found in Tidal forests.
Answer:
Sundari, hogla, garan, gewa, gotpata etc.

Question 41.
Name the economically most important vegetation belt of India.
Answer:
Monsoon deciduous forests.

Question 42.
Name two typical trees
Answer:
Khair and Khajuri.

Question 43.
Name two important festivals of the christian community
Answer:
Christmas, Good Friday.

Question 44.
Which tribe has a Tibetan origin ?
Answer:
Bhutia

Question 45.
When do we observe our Republic Day?
Answer:
26th January

Question 46.
What is your mother language?
Answer:
Nepalee

Answer the following questions briefly: (2 mark each)

Question 1.
Define the term soil.
Answer:
Soil is a thin layer of loose material of small rock particles and rotting organic matter that covers much of the world’s land surface.

Question 2.
Why is soil important?
Answer:
Soil supports all forests, grasslands and crops from which all living creatures of the earth drive their food.

Question 3.
Name the four main elements found in soils.
Answer:
Silica, clay, chalk and humus.

Question 4.
State the factors on which the formation of soils depends.
Answer:

• Parent material
• Tropgraphy
• Climate.

Question 5.
State three types of soils on the basis of its composition.
Answer:

• Sandy, soils
• Clayey soils
• Loamy soils.

Question 6.
Name two main types of alluvial soils found in Northern India.
Answer:

• Khadar and
• Bangar soils.

Question 7.
State the local names for Khader and Bangar soils.
Answer:

• Khadar soil = Bet (local name)
• Bangar Soil = Dhaia (local name)

Question 8.
Name two important crops or grains grown in alluvial soils.
Answer:
Rice and wheat.

Question 9.
Which soils are found on the periphery of Deccan plateau ?
Answer:
Red soils.

Question 10.
Which soil is most widespread over Penisular India?
Answer:
Red soils.

Question 11.
Name two states where red soils are mostly found.
Answer:
Tamil Nadu and Chhattishgarh.

Question 12.
What is the appearance of regur soils ?
Answer:
Blak.

Question 13.
Name two states where black soils are found.
Answer:
Maharastra and Madhya Pradesh.

Question 14.
Stat the two other names for black soils.
Answer:
Cotton soil and Regur soils.

Question 15.
How are black soils formed?
Answer:
By weathering of vocanic rocks of Deccan trap.

Question 16.
In which type of climate are laterite soils formed?
Answer:
Tropical monsoon climate.

Question 17.
State three states where laterite soils are found.
Answer:
Andhra Pradesh, Tamil Nadu and Orisha.

Question 18.
For which crops are laterite soils best suited?
Answer:
For plantation crops.

Question 19.
Which two types of soils are found in Sandy deserts?
Answer:
Saline and alkaline.

Question 20.
For which crop mountain soils are best suited?
Answer:
For plantation crops like tea.

Question 21.
What is the cause of sheet erosion?
Answer:
Cultivation on hill slopes.

Question 22.
What are chos?
Answer:
Choose are seasonal streams in foothills of siwaliks.

Question 23.
Define agriculture?
Answer:
Agriculture is the practice, art and science of cultivating the land and raising crops for food.

Question 24.
State any two Rabi crops.
Answer:
Wheat and Oilseeds.

Question 25.
What kind of soil is best suited for cultivation of rice?
Answer:
Alluvial loans in river valleys and deltas.

Question 26.
Name three millets.
Answer:
Jowar, Bajra, Ragi.

Question 27.
Name two states which are the leading producers of millets.
Answer:
Maharashtra and Andhra Pradesh.

Question 28.
Name three states which produce long staple cotton.
Answer:
Punjab, Haryana and Rajasthan.

Question 29.
Why is Maharastra leading cotton producing state in the country?
Answer:
Due to suitable black soils.

Question 30.
Why are millets called dry crops?
Answer:
Millets are grown in dry areas. The moisture is not sufficient for the growth of other crops. So these are known as dry crops.

Question 31.
Give two aspects of Green Revolution which helped increase the yield of wheat.
Answer:

• Use of better varieties of wheat
• Highly mechanised farming.

Question 32.
What is commercial farming?
Answer:
When cultivation is done on large farms to earn from each crops, it is called commercial farming.

Answer the following questions briefly: (2/3 mark each)

Question 1.
Define the term soil.
Answer:
Soil is a thin layer of loose material of small rock particles and rotting organic matter that covers much of the world’s land surface.

Question 2.
Name the four main elements found in soils.
Answer:
Silica, clay, chalk and humus.

Question 3.
Explain the importance of soils.
Answer:
Many human and economic activities depend on soils. All out food comes directly or indirectly from soils. Livestock farming depends upon raising of grass on different soils. Soils have affected the march of civilisations. Ancient civilisations developed in fertile river valleys. Fertile soils attract human settlements. Density of population depends upon soil fertility and productivity.

Question 4.
Name any five methods to check soil erosion.
Answer:
The following methods are adopted to guard against soil erosion :

• Afforestation and reafforestation
• Controlled grazing
• Terraced ploughing
• Contour bunding
• Rotation of crops.

Question 5.
What are the characteristics of laterite soils? Name one region where it is found.
Answer:

• The laterite soils are of brick colour.
• These are shallow, acidic and less fertile.
• These are less fertile due to leaching of soil.
• These are poor in nitrogen, potash but rich in iron.
• These are found in Tamil Nadu.

Question 6.
Mention two characteristics of red soil.
Answer:

• These are poor in nitrogen and humus.
• Their colour is red due to high iron content.

Question 7.
How many types of soils are found in India ?
Answer:
There are five main types of soils in India :

• Alluvial soils
• Black soils
• Laterite soils
• Red soils
• Desert soils.

Question 8.
In what ways does regur soil help agriculture?
Answer:

• It can retain moisture and become wet. When dry, it can be easily ploughed.
• It is highly fortile and suitable for cultivation of cotton.

Question 9.
Soil erosion has become a pressing problem in India.
i. What is soil erosion ?
ii. Give two reason for this soil erosion.
iii. Give two methods used to prevent soil erosion.
Answer:
i. Soil erosion is the destruction and removal of topsoil by running water, wind, etc.
ii. Deforestation and overgrazing.
iii. Afforestation and controlled gazing.

Question 10.
Name the three types of alluvium and state the areas of their occurence.
Answer:

• Deltaic alluvium-Gange delta.
• Coastal aluvium-Deltas of east-coast.
• Inland alluvium-Punjab plains.

Question 11.
Why are the alluvial soils of Deccan coastal plain darker in colour ?
Answer:
Most of the Deccan rivers rise from western ghats. These flow through black soil region. These carry a lot of black soil to Delta which makes it dark. For example, the soils of Godavari and Krishna valley.

Question 12.
Why are red soils red in colour ?
Answer:
The red colour is due to iron content. The process of oxidation makes it red.

Question 13.
Why is black soil easily friable ?
Answer:
During dry period, cracks appear in black soils. These help in acration of soils. So it is easy to cultivate these.

Question 14.
State the conditions favouring the formation of laterite soils. :
Answer:

• Monsoon climate.
• Alternating wet and dry seasons.
• High temperatures and high rainfall.
• Leaching of soils.

Question 15.
State three factors which determine kind of soil erosion.
Answer:

• Climate
• Slope
• Nature of cultivation.

Answer the following questions briefly: (5 mark each)

Question 1.
Compare Black soils and Red soils.
Answer:

Black Soil	Red Soil
1. This soil has been formed by the decomposition of lava rocks.	1. This soil is formed by the decomposition of those rocks which have iron contents.
2. This soil contains potassium, iron, magneism and humus.	2. This soil does not contain magnesium, phosphours, nitrogen and lime. It has large amount of iron oxide.
3. Black soil can retain moisture for a long time and does not require much irrigation.	3. It cannot retain moisture for long. Crops can be grown during the rainy season.
4. This soil is very productive.	4. It is not very fertile.

Question 2.
Distinguish between Bangar and Khadar.
Answer:
Distinction between Banar and Khadar:

Bangar	Khadar
1. The older alluvium of the plains is called Bhangar.	1. The younger alluvium of the plains is called Khadar.
2. This area stands above the level of the flood plain.	2. Flood wate spreads a new layer over it every year.
3. It is composed of calcareous kankars and clay.	3. It is composed of fertile alluvium.
4. The flood water does not reach here.	4. These are actually flood plains of the rivers.
5. In some areas, local name Dhata is given to this.	5. In some areas local name Betis given to this.

Identify the correct answers (MCQ): (1 mark each)

Question 1.
The tropic of cancer passes through ………….
a. Rajasthan
b. Odisha
c. Chhattisgarh
d. Assam
Answer:
c. Chhattisgarh

Question 2.
Northern most point of India is ………….
a. Kibithu
b. Guhar Moti
c. Indira Col
d. Indira Point
Answer:
c. Indira Col

Question 3.
The state of India that shares boundary with maximum states
a. Uttar Pradesh
b. Kerala
c. Andhra Pradesh
d. Tripura
Answer:
a. Uttar Pradesh

Question 4.
The easternmost longitude of india is ………….
a. 97º 25′ E
b. 68º 7′ E
c. 77º  6′ E
d. 82º  32′ E
Answer:
a. 97º 25′ E

Question 5.
India is located in the ………….
a. northern hemisphere
b. southern hemisphere
c. north-western hemisphere
d. north-eastern hemisphere
Answer:
a. northern hemisphere

Question 6.
Gulf of Mannar and Palk Strait separates ……………. from India.
a. Pakistan
b. Maldives
c. Sri Lanka
d. Nepal
Answer:
c. Sri Lanka

Question 7.
Here the largest neighbouring country of India is ………….
a. Sri Lanka
b. Bhutan
c. Nepal
d. Bangladesh
Answer:
d. Bangladesh

Question 8.
The smallest neighbouring country of India is ………….
a. Sri Lanka
b. Bhutan
c. Nepal
d. Bangladesh
Answer:
b. Bhutan

Question 9.
The State Reorganisation Commission was set up in ………….
a. 1953
b. 1956
c. 1965
d. 1972
Answer:
a. 1953

Question 10.
India lies in the continent of …………..
a. Asia
b. Europe
c. Africa
d. North America
Answer:
a. Asia

Question 11.
The most continuous Himalayan range is ……..
a. Himachal
b. Himadri
c. Shiwaliks
d. Tethys Himalayas
Answer:
b. Himadri

Question 12.
The largest and longest mountain system of India is the ……..
a. Aravalli range
b. Anaimalai range
c. Nilgiri range
d. Himalayan range
Answer:
d. Himalayan range

Question 13.
The Thar desert lies to the west of which range?
a. Aravalli
b. Vindhya
c. Satpura
d. Western Ghats
Answer:
a. Aravalli

Question 14.
The oldest landmass of India is the …………
a. Deccan Plateau
b. Alluvian plain
c. Himalayan range
d. Rajasthan desert
Answer:
a. Deccan Plateau

Question 15.
The highest region of the Himalayas is …………
a. Gangotri
b. Shiwalik
c. Himadri
d. Himachal
Answer:
c. Himadri

Question 16.
Highest peak of Deccan plateau or Southern India is …………….
a. Dodabeta
b. Patkoi
c. Anaimudi
d. Gurushikhar
Answer:
c. Anaimudi

Question 17.
Name the coast where the lagoons are locally known as Kayal …………
a. Malabar
b. Konkan
c. Coromandal
d. Karnataka
Answer:
a. Malabar

Question 18.
The Nilgiris are part of the ……..
a. Eastern Ghats
b. Western Ghats
c. Vindhyachal
d. Tamil Nadu Hills
Answer:
b. Western Ghats

Question 19.
Lakshadweep islands are located in …….
a. Bay of Bengal
b. Arabian Sea
c. Indian Ocean
d. Persian Gulf.
Answer:
b. Arabian Sea

Question 20.
Purvachal refers to the …….
a. Eastern Ghat
b. Western Ghat
c. North-east frontier mountain range
d. Chota Nugpur
Answer:
c. North-east frontier mountain range

Question 21.
Which of the following does not have influence over the climate in India?
a. Nearness of equator
b. Presence of Indian Ocean
c. Monsoons
d. Ocean currents
Answer:
d. Ocean currents

Question 22.
The place in India receiving the lowest rainfall is-……….
a. Jaisalmer
b. Bikaner
c. Jodhpur
d. Leh
Answer:
d. Leh

Question 23.
The Wettest place found in the north-east of India is-……….
a. Jacobabad
b. Mawsynram
c. Cherrapunji
d. Kohima
Answer:
b. Mawsynram

Question 24.
Monsoons are winds.
a. local
b. seasonal
c. permanent
d. temporary
Answer:
b. seasonal

Question 25.
India lies to the north and south of the-……….
a. Arctic Circle
b. Tropic of Cancer
c. Equator
d. Tropic of Capricorn
Answer:
b. Tropic of Cancer

Question 26.
The retreating south-west monsoon does not affect-……….
a. Tamil Nadu
b. Odisha
c. Andhra Pradesh
d. Uttar Pradesh
Answer:
d. Uttar Pradesh

Question 27.
The place that gets rainfall from the western disturbances is-……….
a. Ahmedabad
b. Mumbai
c. Srinagar
d. Kolkata
Answer:
c. Srinagar

Question 28.
The place which has lowest mean temperature in January is-
a. Kolkata
b. Lucknow
c. Mumbai
d. Srinagar
Answer:
d. Srinagar

Question 29.
Tamil Nadu gets most of its rainfall in the months of-……….
a. March-April
b. July-August
c. October-November
d. December-January
Answer:
c. October-November

Question 30.
The state of Assam falls in the region of-……….
a. heavy rainfall
b. moderate rainfall
c. very heavy rainfall
d. scanty rainfall
Answer:
c. very heavy rainfall

Question 31.
One of regions that receives rainfall from the north-easterly monsoon is……….
a. Assam
b. Kerala
c. West Bengal
d. Tamil Nadu
Answer:
d. Tamil Nadu

Question 32.
At which place will you find maximum sunlight in December ?
a. Kanyakumari
b. Pune
c. Kolkata
d. Lah
Answer:
a. Kanyakumari

Question 33.
The minimum forest cover nessary to maintain ecological balance is………..
a. 50% of the total land area
b. 42% of the total land area
c. 32% of the total land area
d. 33 % of the total land area
Answer:
d. 33 % of the total land area

Question 34.
How much area of the country is under forest
a. 22%
b. 33%
c. 42%
d. 48%
Answer:
a. 22%

Question 35.
Tidal forests are known as …………
a. Tripical evergreen forests
b. Dry deciduous forest
c. Mangrove forests
d. Semidesert forests.
Answer:
d. Semidesert forests.

Question 36.
Teak, Sal, Sandalwood are examples of ………..
a. dry deciduous
b. Wet deciduous
c. desert forest
d. mangroves forest
Answer:
b. Wet deciduous

Question 37.
Rosewood, gurjan, chaples etc. are examples of ………..
a. Tropical evergreen
b. Wet deciduous
c. dry deciduous mangrove forest
d. Tropical evergreen forest
Answer:
d. Tropical evergreen forest

Question 38.
Oak, pine, fir etc. are examples of ………..
a. Tropical evergreen
b. Deciduous forest
c. mountain forests
d. Desert forest
Answer:
c. mountain forests

Question 39.
Indian Forest Research centre situated in the town of ………..
a. Delhi
b. Chennai
c. Dehradun
d. Kolkata
Answer:
c. Dehradun

Question 40.
The National Forest law of India was passed in-……………
a. 1952
b. 1962
c. 1972
d. 1982
Answer:
d. 1982

Question 41.
The most important food crop of India is: …………
a. Tea
b. Rice
c. Pulses
d. Millets
Answer:
a. Tea

Question 42.
One of the Kharif crops is …………..
a. Gram
b. Wheat
c. Rapeseed
d. Rice
Answer:
d. Rice

Question 43.
One of the rabicrops is…………
a. Wheat
b. Rice
c. Jowar
d. Jute
Answer:
a. Wheat

Question 44.
Which region in India is known as the ‘Rice Bowl of India’.
a. Indo-Gangetic plain
b. Krishna Godavari Delta Region
c. North-east region
d. Kerala and Karnataka
Answer:
a. Indo-Gangetic plain

Question 45.
Which of the following is the second most important crop of India ?
a. Wheat
b. Rice
c. Jowar
d. Bajra
Answer:
a. Wheat

Question 46.
Which of the following states is the leading producer of tea ?
a. West Bengal
b. Sikkim
c. Assam
d. Karnataka
Answer:
c. Assam

Question 47.
The Kharif season beings
a. With the onset of South-west
b. Monsoon
c. In December
d. In March
Answer:
a. With the onset of South-west

Question 48.
The largest producer of rice in India is…………
a. Bihar
b. Tamil Nadu
c. West Bengal
d. Karnataka
Answer:
c. West Bengal

Question 49.
Which state has the largest producer of sugarcane in India is-…………
a. Bihar
b. Punjab
c. Maharastra
d. Uttar Pradesh
Answer:
d. Uttar Pradesh

Question 50.
Central Sugarcane research centre is located at…………
a. Kanpur
b. Allahabad
c. Lucknow
d. Banaras
Answer:
c. Lucknow

Question 51.
Cotton Research Centre is 10cated at…………
a. Kanpur
b. Nagpur
c. Ahmedabad
d. Coimbatore
Answer:
b. Nagpur

Question 52.
Rice cultivation require temperature between
a. 15°-20°C
b. 20°-30°C
c. 30°-35°C
d. above 35° C
Answer:
b. 20°-30°C

Question 53.
Wheat cultivation requires rainfall between
a. 50-100 cm
b. 100-150 cm
c. 150-200 cm
d. 200-250 cm
Answer:
a. 50-100 cm

Question 54.
The second largest tea producing state of India is …………
a. Assam
b. Tamil Nadu
c. West Bengal
d. Karnataka
Answer:
c. West Bengal

Question 55.
Tribes are also known in India as ……
a. Adivasis
b. Upajatis
c. Gonds
d. Sanbthals
Answer:
a. Adivasis

Question 56.
Bow men of Rajasthan is called to……
a. Gonds
b. Bhils
c. Jarawas
d. Santhals
Answer:
b. Bhils

Question 57.
Tribes of Himachal Pradesh
a. Chanchu
b. Khasis
c. Munda
d. Kinnaur
Answer:
d. Kinnaur

Question 58.
Chanchu adivasis are inhabitant of …..
a. Kerala
b. Tamil Nadu
c. Rajasthan
d. Andhra Pradesh
Answer:
d. Andhra Pradesh

Fill in the blanks with the correct words: (1 mark each)

1. According to size, India stands ___________ in the world.
Answer: 7th

2. Eastern most point in India is ___________
Answer: Kibithu

3. ___________ is the largest province or state in area in India.
Answer: Rajasthan

4. ___________ is the smallest state in India.
Answer: Goa

5. ___________ is the newest state in India.
Answer: Telangana

6. Southern most point of india is ___________ of Andaman and Nicobar islands, previously it was called Pygmalion Point.
Answer: Indira Point

7. The number of Indian states at present is ___________
Answer: 29

8. India covers an area of ___________ sq. km.
Answer: 32,87,782

9. _______ on Karakoram is the highest peak of India.
Answer: K2

10. ______ is the highest plateau in India.
Answer: Ladakh

11. The ______ range lies between the Narmada and Tapi.
Answer: Satpura

12. ______ is well-known pass to the south of Nilgiris connecting Kerala to Tamil Nadu.
Answer: Palghat

13. The ______ of Kashmir is the longest and the most important Himachal range.
Answer: Pir Panjal

14. The highest peak in India’s Himalayan mountain region is ______
Answer: Kangchenjunga

15. The ______ plateaus constitute the largest physiographic division of the country.
Answer: Peninsular

16. Northern section of the Western Ghat range is known as ______
Answer: Sahyadris

17. ______ is the largest lagoon of Malabar coast.
Answer: Vembanad

18. The middle himalayas are known as ______
Answer: Himachal

19. Rajasthan is in the region of ______ rainfall.
Answer: Scanty

20. The region getting rainfall during the south-west monsoon and northeast monsoon______
Answer: East Coast

21. The climate of India is described as ______ monsoon.
Answer: Tropical

22. The ______ monsoon winds flow form land to sea.
Answer: Retreating

23. The rainfall with violent thunder and lightning is known as ______ of monsoon.
Answer: Burst

24. Tamil Nadu gets rainfall from the ______ monsoon wind.
Answer: north-east

25. India gets rainfall from south west monsoon between June and ______
Answer: July

26. Punjab gets rainfall in winter due to the cyclonic depressions originated from the …………
Answer: September

27. The ______ soils of the delt are more fertile than the coastal ______
Answer: alluvial, alluvium

28. Khader is the ______ alluvium where as bhangar is ______ alluvium.
Answer: newer

29. Black soil is also called as ______ soil.
Answer: regur

30. Rajasthan has ______ soil.
Answer: arid or desert

31. Black soils are fertile because they have ______
Answer: magnesium carbonate

32. Laterite soils are rich in ______ and iron oxides.
Answer: aluminium

33. A huge amount of soil erosion takes place during mineral ______
Answer: extraction

34. Planting trees on barren hill slopes is one of the methods of soil ______
Answer: conservation

35. Wildlife refers to wild plants and wild ______
Answer: animals

36. Affestation means forest ______
Answer: expansion

37. ______in India where tropical evergreen forests are found.
Answer: The western slopes of western ghats

38. The total forested area in India is about ______ million hectares.
Answer: 63.73

39. ______ March is observed as “World Forest Day’.
Answer: 21

40. Teak and Sal are the most important trees of ______forest in India.
Answer: Monsoon

41. There is a close relationship between ______ and vegetation.
Answer: Climate

42. The annual festival of tree planting called ______ is celebrated to make the people aware of the utility of forests.
Answer: Van Mahotsav

43. Summer : ______ Winter: Orange
Answer: Mango

44. Mountainous Temperate Forest: Pine. ______Teak
Answer: Tropical Deciduous Forest

45. Tea cultivation: slopes. Paddy cultivation: ______
Answer: Plains

46. Kaziranga National Park : Rhinoceros.Gir National Park: ______
Answer: Lion

47. Mangrove: West Bengal.Mountainous Temperate Forests: ______
Answer: Kashmir

48. High Blood Presure : ______ Malaria : Cinchona.
Answer: Sarpagandha

49. Alluvial Soil : ______ Black soil : Cotton.
Answer: Jute

50. A food crop that grows under stagnent water condition is ______
Answer: Rice

51. India stands next to in the called ______ crops.
Answer: China

52. Crops cultivated for sale are called ______ crops.
Answer: Cash

53. The crop referred to as golden fibre is ______
Answer: Jute

54. ______ is the staple food of south Indians.
Answer: Rice

55. ______ is cultivated both as a Kharif and rabi crop.
Answer: Sesamum

56. The Beverage crops are and ______
Answer: Tea, coffee

57. Green Revolution has introduced programmees of ______ agriculture.
Answer: intensive

58. Father of the nation is ______
Answer: Mahatma Gandhi

59. Independence day is observed on ______ in India.
Answer: 26th January

60. The main occupation of Todas is ______ rearing.
Answer: Cattle

61. ______ are the native people of South Andaman.
Answer: Jarawas

62. ______ is the main occupation of Bhutia.
Answer: agriculture

If the sentence is true, write ‘T’ and if false write ‘F’ against the following. (1 mark each)

1. North-eastern hills of India are together known as Purbachal.
Answer: True

2. Siachen is the longest glacier in India.
Answer: True

3. The Western coastal plain lies along the Bay of Bengal.
Answer: False

4. The Narmada Valley lies between the Vindhyas and Satpura.
Answer: True

5. The Gangotri and the Yamunotri glaciers are found in the Himadri.
Answer: True

6. Mangrove vegetation groups in the black soils of Deccan plateau region.
Answer: False

7. Khadar soil is very much fertile.
Answer: True

8. In India red soil mainly originates from granite and gneiss rocks.
Answer: True

9. The new alluvium of the river valley is known as regur.
Answer: False

10. Soil gets eroded indirectly by too much animal grazing.
Answer: True

11. Due to soil erosion, the upper layer rich in organic matter, is lost and soil becomes infertile.
Answer: True

12. In order to check soil erosion step cultivation should be practiced on the hill slopes.
Answer: True

13. The roots of trees do not hold the soil tight.
Answer: False

14. The tropical deciduous forests are the most important forests of India.
Answer: True

15. Social forestry is a plan for deforestation as well as consumption.
Answer: False

16. Tidal forests are found on the estuaries and fringe of deltas along the east coast of India.
Answer: True

17. The one-horned rhinoceros is found nowhere in the world except in Assam, India.
Answer: True

18. Lions, in Asia, are found only in the Gir Forest of Gujarat.
Answer: True

19. India has over 500 species of animals and 1200 species of birds.
Answer: True

20. Tropical evergreen forests in India are found in the areas with under 80cm of annual rainfall.
Answer: False

21. There are about 88 national parks in India.
Answer: True

22. Wheat is a Kharif crop and it thrives well is hot and humid climate.
Answer: False

23. The coarse grains like Jowar, Bajra and ragi are together called as millets.
Answer: True

24. India has the largest are a under pulses.
Answer: True

25. Crops cultivated for food are termed as cash crops.
Answer: False

26. Jute is an important cash crop in the north eastern parts of India.
Answer: True

27. India has been the largest producer and consumer of black tea in the world.
Answer: True

28. Todas inhabit the Nilgiri hills.
Answer: True

29. Khasis follow Christianity.
Answer: True

30. Santhals are one of the largest tribe in India.
Answer: False

31. The chief occupation of Munda is cultivation.
Answer: False

32. Santhal adivasis have Oichiki script.
Answer: True

Match the Following (1 mark each)

Question 1.

1. The cold weather season	a. October-November
2. The hot weather season	b. December-February
3. The south-west monsoon season	c. March-May
4. The north-east monsoon season	d. September-March
	e. June-September

Answer:

1. The cold weather season	b. December-February
2. The hot weather season	c. March-May
3. The south-west monsoon season	e. June-September
4. The north-east monsoon season	a. October-November

Question 2.

1. Loo winds	a. Punjab
2. Norwesters	b. Tamil Nadu
3. Blossom showers	c. Rajasthan
4. Break of monsoons	d. Assam and West Bengal
5. Western disturbances	e. Karnataka
	f. Kerala

Answer:

1. Loo winds	c. Rajasthan
2. Norwesters	d. Assam and West Bengal
3. Blossom showers	e. Karnataka
4. Break of monsoons	f. Kerala
5. Western disturbances	a. Punjab

Question 3.

1. Allvial soil	a. Sahyadris
2. Black soil	b. Arid and semi-arid parts
3. Reds oil	c. Jammu and Kashmir
4. Laterite soil	d. Deccan trap
5. Forest and hilly soil	e. Peninsular India
	f. Northern plains
	g. Jhar desert of Rajasthan

Answer:

1. Allvial soil	f. Northern plains
2. Black soil	d. Deccan trap
3. Reds oil	e. Peninsular India
4. Laterite soil	a. Sahyadris
5. Forest and hilly soil	c. Jammu and Kashmir

India: Our Motherland Class 6 WBBSE Notes

Chapter at a Glance

India : The largest democratic country in the world is India. In Asia, India is the leading developing country. India’s latitudinal extent lies between 8°4‘ N and 37° 6‘N, whereas its longitudinal extent lies between 68° 7’E and 97°25‘E. India is the 7 th largest country in the world. Its total area is 32,87,263 sq. km. Delhi is the capital of India.

Physiography of India : India has a colourful beauty in nature. India is a land of rivers, mountains, extensive plains, plateaus, deserts and coastal regions. India, can be divided into five physiographic divisions, such as

• The Northern Mountains
• The Northern Plains
• The Peninsular Plateau or the Deccan Plateau
• The Coastal Plains and
• The Islands.

Rivers of India: The rivers of India are broadly classified into two groups, such as

• The North Indian Rivers and
• The South Indian Rivers.

The North Indian rivers are mainly the Ganga, Brahmaputra, Indus etc. Ganga is the largest and most important river of India. Its total length is 2071km. The South Indian rivers are mainly the Godavari, Krishna, Kaveri etc.

Climate of India : The general climate that can be seen in India is ‘Tropical Monsoon Climate’. Mainly four seasons are there in India Prominently, namely summer, monsoon, autumn and winter. The summer lasts here for much more time than the winter.

About 80% of rainfall in India occurs due to the south-west monsoons. The highest rainfall in the world occurs in Mawsinram near Cherrapunji in Meghalaya (1350cm).

Soils of India : The materials on the earth surface within which horizons or layers have developed is known as soil. The soils of India has divided into 27 types according to their colour, texture, mineral and retentive capacity of moisture. The types of soils are classified into 8 categories, such as

• Alluvial soil,
• Black soil
• Red soil
• Laterite soil
• Desert soil
• Saline soil and
• Mountain soil.

Natural Vegetation of India : In India, about 20.55% land is under forest cover. Natural forests in India can be categorised as

• Tropical Evergreen Rain- Forests
• Tropical Deciduous Forests
• Semi-deserts and deserts vegetation
• Tidal Forests
• Mountain Forests.

Wildlife of India : Various kinds of wild animals and birds are found in the Indian forests. Some of the important animals are lions, tigers, leopards, elephants, bears, rhinoceros etc.

Agriculture of India : India is an agricultural country. About 65% people of India are involved in agriculture. The main crops of India are Rice, Wheat, Maize, Cotton, Jute, Tea, Coffee, Rubber, Sugarcane etc.

Tribes of India : India has the largest tribal peoples (about 84.4 million). They are the poorest and perhaps the most backward in the world. Some of the major tribal groups in India are Gonds, Santhals, Bhils, Khasis, Angamis, Bhutias and Andamanese.

Location :

Introduction : India is the world’s largest democratic country. India is a huge and ancient country. It has its unique culture, heritage and signature, that gives it a classic ‘Indianism’. Probably about 3500 years ago, the country derived its name ‘Bharat’,after the ancient ruler named King Bharat. The ancient Greek people named this land ‘India’, which probably has come from river ‘Indus’.

Location : India is located in the north-eastern hemisphere of the world. It belongs to the continent of Asia. Lying in the southern part, India is an important developing country of Asia, as well as the world.

Latitudinal extent : The main landmass of India lies between 8°4‘ N (Kanyakumari) and 37° 6‘N (Kashmir Border). The Tropic of Cancer (23 \(\frac{1}{2}\)°N) passes through the middle of the country from east to west, cutting it almost into two equal halves.

Longitudinal extent : India lies between 68° 7‘E (western border of Gujarat) and 97° 25‘E (Eastern border of Arunachal Pradesh). The 82 \(\frac{1}{2}\)° E longitude passes through the centre of the country, cutting it into almost equal halves on the east and west. This is also considered as the Standard Meridian, along which, the Indian Standard Time is calculated.

Boundaries
North : The northern boundary is marked by the huge and gigantic Himalayan range. China, Nepal and Bhutan also form parts of the northern boundary.

North West : Pakistan and Afghanistan mark the north-western boundary.

West : The western side of India is bounded by Pakistan and the Arabian Sea.

East : The eastern boundary is constituted by Bangladesh, Myanmar and Bay of Bengal.

South : The southern boundary is marked by the Indian Ocean and Sri Lanka, which is separated from the Indian landmass by the Palk Strait and the Gulf of Mannar.

Size : India is the 7th largest country of the world, after Russian Commonwealth, China, Canada, Brazil, USA and Australia. Total area of this country was 32,87,263 sq. km. of which 37.555 sq. km. was illegally occupied by China, and 78,114 sq. km by Pakistan. It constitutes about 2.4% of total land surface of the earth. Along land surface, the border of India is about 15,200km long. The coastline is about 7516.6km including Andaman and Nicobar and Lakshadweep islands.

Why is India called a ‘peninsular country’ ?
If a landmass is surrounded by sea on three sides and attached to the main landmass on the fourth side, it is called a peninsula. India is surrounded by the Bay of Bengal, Indian ocean and Arabian Sea on the east, south and west respectively. On the north, it is bounded by the Great Himalayan range, Nepal, Bhutan and China. Hence, India is called a ‘peninsular country’.

Why is India called a ‘sub-continent’?
India, together with Pakistan, Nepal, Bhutan, Bangladesh and Sri Lanka is called a ‘sub-continent’. The huge size, huge population, large variety of physical and geographical features, culture, heritage, etc. make the land as diverse as a continent. The usual characteristics of any continent are found in this land. Although not as big as a continent, this huge landmass exhibits ‘unity in diversity’. Hence it is called a ‘sub-continent’.

Some important points

1. Northernmost point of India → Indira Col in Kashmir.
2. Southernmost point of India → Indira Point of Andaman and Nicobar islands. Previously it was called Pygmalion Point.
3. Westernmost point of India → Guhar Moti of Gujarat.
4. Eastern most point of India → Kibithu of Arunachal Pradesh.
5. Time difference between the eastern and western margins of India → about 1 hour 56min.
6. Southernmost point of India’s main landmass → Kanyakumari of Tamil Nadu.
7. Indian state that shares boundary with maximum number of states → Uttar Pradesh, touches 8 state boundaries.
8. State touching maximum number of international boundaries → West Bengal, Arunachal Pradesh, Jammu and Kashmir.

Delhi is also the Capital of India.

• The biggest in area – Rajasthan.
• The Smallest State – Goa.
• Smallest Union Teritory – Lakshadweep.

The basis of reorganisation of states in India : Importance is laid on five points

• Language
• Advantage from administrative point as well as development plans
• Similarity of economic and geographic features
• Economic stabitity and
• Physical and Geographic similarities.

Some important borders and borderlines of India :

Border	Countries sharing the border
1. Durand line	India-Afghanistan (1896)
2. Macmohan line	India-China (1914, after Simla Treaty)
3. Radcliffe line	India-Pakistan (1947, about 8000 km long, including East Pakistan now Bangladesh).
4. 24th Parallel	India-Pakistan (demanded by Pakistan)
5. 8° Channel	Minicoy—Maldives Islands.
6. 9° Channel	Lakshadweep-Minicoy islands.
7. 10° Channel	Andaman-Nicobar Islands.
8. Duncan Passage	Bigger Andaman-Smaller Andaman
9. Great Channel	Andaman Nicobar-Sumatra
10. Line of Control(LOC)	India-Pakistan (Near Kashmir)
11. 28th Parallel	Between part of Kashmir occupied by India and part of Kashmir occupied by Pakistan.

Cultural Heritage of India :
Important cultural heritage sites of India are

a. Historical and cultural heritage sites :

• Humayun’s tomb in Delhi
• Taj Mahal at Agra
• Agra Fort
• Khajuraho
• The caves of Ajanta and Elora.

b. Group of Monuments at Mahabalipuram, Konark Sun Temple, Churches and Convents of Goa, Fatehpur Sikri etc.

c. India’s World natural heritage sites are Sundarbans, the Nanda Devi peak, Kaziranga reserve forest etc.

Relief Or Physiography Of India

Introduction : India is a land of mighty rivers, lofty mountains, extensive plains, vast plateaus, deserts and coastal regions. Based on the variety of physical features, India can be divided into the following physiographic divisions :

1. The Northern Mountains
The Location and Extent : The northern part of India is consisted of the ranges of Karakoram and the Himalayan mountains. The northern mountains of India have two mountain systems.

A. The Karakoram Ranges and
B. The Himalayan Ranges Delta

A. The Karakoram Ranges: The Karakoram is bounded on the north-east by the Tibetan plateau, on the north by the Pamir plateau and on the south by rivers Indus, Gilgit and Shyok. These are very high mountains. Godwin Austin (8,611m) is the highest peak of Karakoram. So it is known as K2 (King of Karakoram). It is the India’s highest and the world’s second highest peak. Baltoro (60 km long) in Karakoram is the home of some of the largest glaciers of the world. The Siachen (90m), the longest glacier of India lies here.

B. The Himalayan Ranges: The Himalaya means the Abode Snow. It extends from the Nanga Parbat of Jammu and Kashmir in the west to Namcha Barwa of Arunachal Pradesh in the east. The shape of the Himalaya is like an arc. It it about 2500 km. long and its width varies from 160 to 450km. Divisions of the Himalayas : The Himalayas may be classified into

• Physiographic Divisions and
• Regional Divisions.

Physiographic Divisions : The Himalayas are not a single, continuous  chain of mountains., but a series of parallel or converging ranges. The Himalayas can be divided into three main ranges that run parallel to each other.

a. The Greater Himalayas or the Himadri: It is the highest part of the Himalayas. The average elevation of the Himadri is 6,000m. and it is permanently covered with snow. Mount Everest (8,848m), the highest peak in world is located here. There are some other peaks, such as Kangchenjunga (8,598m, the world’s third highest peak), Dhaulagiri (8,172 m.), Nanga Parbat ( 8,126m), Annapurna (8,076 m.), Nandadevi (7,817m) etc. The Gangotri and the Yamunotri glaciers are found in the Himadri.

Kangchenjunga is the highest peak in India because Mt. Godwin Austin is in Jammu and Kashmir of India is an area under debated occupation of Pakistan and China.

b. The Lesser Himalayas or Himachal : It is a massive mountainous tract about 75km. wide and lies south of Himadri. It has an average elevation of 4,500m. This mountain belt is highly dissected. Many of the hill stations, such as Simla, Nainital, Mussoorie, Darjeeling are situated in this belt.

c. The Outer Himalayas or Shiwalik : It is the southernmost range of the Himalayas. It forms the foothills of Himalayan range. It is 600 to 1500m. high with a width ranging from 15 to 50 km. It is a chain of low-lying hills. It is not a continuous range. There are broad longitudinal valleys in the Shiwaliks known as Doons. Dehradun is one of such valleys. Foot hills of Shiwaliks are known as Terai.

(ii) Regional Divisions of the Himalayas : The Himalayas have been divided into three regional divisions. These are :
a. Western Himalayas
b. Central Himalayas (lies in Nepal) and
c. Eastern Himalayas.

a. Western Himalayas : The Western Himalayas are again subdivided into four sub-regional divisions such as

• North Kashmir Himalaya
• South Kashmir Himalaya
• Himachal Himalaya and
• Uttaranchal Himalaya.

It is called the Trans-Himalayas or the Tethys Himalayas. They are made up of the Ladakh Range, Zanskar Range and the Pirpanjal Range. Ladakh is the highest plateau of the world. The important mountain passes in this region are Zojiia between Srinagar, Leh and Shipkila on Indo-China border.

b. Central Himalayas : They extend in Nepal.
c. Eastern Himalayas: They are in the north: West Bengal, Sikkim and Arunachal Pradesh in India and Bhutan. The Nathula pass lies between India and Tibet.

The north-eastern region : This comprises the 7 sister states of Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland and Tripura. It comprises about 8% of India’s size. Physiographically, the region is a part of the Eastern Himalayas. Low hills like Garo, Khasi, Lushai, Patkai etc. make \(\frac{2}{3}\) of the hilly region, intercepted by valley and plains. E.g.-The Brahmaputra and Barak river valleys.

2. The Northern Plains :
They lie to the south of the Himalayas. They extend from the eastern Rajasthan plains in the west to the Brahmaputra valley in the east for a distance of about 2,500 km. They are 145 to 480 km broad. They are also known as the Great Northern plain. It consists of the following plains :

a. The Plains of Rajasthan: The areas on the northwest, west and south-west of the Aravallis are known as the western plains of Rajasthan. The region is marked by various types of erosional features. The plain is basically stony, and sloppy from the foothills of the Aravallis to the north-west. Rivers Banas, Mahi and numerous tributaries drain into the region. The deeply dissected area of Chappan region in the south-eastern part is locally called ‘Bagar’. Southern and south-eastern Rajasthan is mostly a plateau.

b. The Punjab-Haryana Plains (Indus Basin) : They are drained by the tributaries of river Indus, Ravi, Beas and Sutlej. These are flat plains with an average elevation of 200 to 240m. These fertile plains include the Bari Doab (between Ravi and Beas rivers) and Bisht Doab (between Beas and Sutlej).

c. The Ganga Plains: The Ganga plains of U.P., Bihar and West Bengal occupy an area of 3.57 Lakh sq. km. It lies between the Yamuna catchment area in the west to the Bangladesh border in the east. The several kinds of topographical features seen here are-Bhabar, Khadar, Bhangar, Terai, natural levees, abandoned river courses, badlands, etc.

d. The Brahmaputra Plains : It is a low flat land averaging in elevation less than 10m. above sea level.

3. The Peninsular Plateau or The Deccan Plateau:
It is bordered by the Satpura Range in the north, the Western Ghats in the west and the Eastern Ghats in the east. It is of triangular shape. Significant features of the Deccan Plateau are-

• Satpura Range : It lies on the extreme north of the Deccan plateau. Dhupgarh (1,350m) is the highest peak
• Maharashtra Plateau : It is made up of lava. It is called lava plateau.
• Telangana Plateau : It is a rolling surfaced plateau with intervening shallow depression. It is in Andhra Pradesh
• Karnataka Plateau: The plateau is divided into Malnad and Maidan. The Malnad is hilly, and dissected into deep valleys; while the Maidan is formed of rolling plains with low granite hills
• The Western Ghats or the Sahyadris : With an average height of 1200m these run almost parallel to the west coast for about 1600 km. The Sahyadri

(Maharashtra), the Nilgiri, the Annamalai and the Cardamom Hills are all collectively known as the Western Ghats. Anaimudi (2,695m) of Annamalai is the highest peak of the Deccan Plateau. Dodabeta (2,637m) is the highest peak of Nilgiri. There are several passes in the Western Ghats.

The important ones are the Thal Ghat and the Bhor Ghat. Pal Ghat lies south of the Nilgiri Hills. Gersappa or Jog falls (250m) India’s highest waterfall is located in the Sahyadris on the river Sharavathi.

• The Eastern Ghats : They form the eastern edge of the Deccan Plateau. They are lower in

4. The Coastal Plains:
The coastal plains of India are divided into two parts, (a) The Western  Coastal Plains: These plains are confined to a narrow belt of about 10 to 20 km. wide stretching between the Arabian sea and the Western Ghats, and extending from Kanyakumari to Surat for about 1500 km.

Kutch and Kathiawar peninsula lie at their northern end. The western coastal plain has many estuaries and lagoons. The west coast is known as the Konkan Coast in Maharashtra, the Karnataka Coast in Karnataka and the Malabar Coast in Kerala. The Gujarat plain is the broadest part of the west coastal plains. These coastal plains consist of two peninsulas.

i. The Kachchh Peninsula : It is a desolate and isolated raised platform covered with sand, sand dunes and mud-flats. It also has a marshy saline lowland which is known as Rann.

ii. The Kathiawar Peninsula : Traditionally it is known as Saurashtra. Its central part is an elevated highland with hills. The Girnar and Gir hills are the most prominent. Gorakhnath (1,117m) is the highest peak of Girnar hills.

b. The Eastern Coastal Plains : These extend from the mouth of Hooghly river to Kanya-kumari. These plains have an average width of 120 km. These are known as the Northern Circars north of the delta of the Godavari and the Coromondal Coast to the south of the delta.

5. The Islands:
The important islands of India are :

a. The Andaman and Nicobar islands : They are located in the Bay of Bengal. They are a group of 324 islands. Saddle Peak (750m) in North Andaman is the highest peak in this region. Barren Island is the India’s only active volcano.

b. Lakshadweep : It is built mainly of corals and situated in the Arabian sea.

Rivers Of India

Based on the characteristics, the rivers of India can be broadly classified into two groups:
(A) The North Indian Rivers and
(B) The South Indian Rivers.

1. The North Indian Rivers
Introduction: The North Indian rivers are comparatively younger in age than the South Indian rivers. They start from the Himalayas and 70% of the water flow down into seas. The main rivers are Ganga, Brahmaputra and Indus. About 61% of total water of the rivers of India flow through the Ganga and Brahmaputra. The main North Indian rivers are discussed below.

A. River Ganga: Ganga is the largest and most important river of India. Of the total length, 2,071 km of the river flows through India. All the 3 phases, i.e., youth, maturity and old age, are present in the river. Hence, it is called an ideal river.

Upper Course: The Bhagirathi river starts from Gomukh (6,600m) of the Gangotri glacier. The rivers Alakananda and Mandakini meet at the Rudra Prayag and their joint flow meets with river Bhagirathi at the Dev Prayag. The joint flow of river Alakananda, Mandakini and Bhagirathi is known as river Ganga. The upper course of the Ganga extends from Gomukh to Haridwar for about 320km.

Middle Course: The Middle course of the Ganga extends from Haridwar to Dhulian of West Bengal. The main tributary of Ganga is river Yamuna, which rises in the Kumaun Himalayas from the Yamunotri glacier and meets river Ganga at Allahabad (Prayag). The left bank tributaries of Ganga are Gomti, Ghaghara, Ram Ganga, Gandak, Buri Gandak, Kosi, etc. The main right bank tributaries are Yamuna and Sone. Tributaries of river Yamuna are Chambal, Betwa, Ken, etc.

Lower Course : After entering West Bengal at Dhulian, the river Ganga bifurcates into river Bhagirathi and river Padma near Giriyar. The Padma enters Bangladesh and flows through the country into the Bay of Bengal. The Bhagirathi, also known as river Hooghly flows southward through West Bengal before meeting the Bay of Bengal.

The right bank tributaries of river Bhagirathi-Hooghly are Brahmani, Dwarka, Mayurakhsi, Ajay, Damodar, Rupnarayan, Kangsabati, etc. The left bank tributaries are-Jalangi, Churni, Ichhamoti, etc.The delta formed by the river Ganga at the mouth of the Bay of Bengal is the largest delta of the world.

B. River Brahmaputra : The river Brahmaputra rises from the Chemayungdung glacier near Manas Sarovar of the Himalayas of the total length of 2,900km, 885km flows within India. Initially known as Tsang-Po, it flows over Tibet plateau for 1,500 km and enters Arunachal Pradesh as river Dihang.

This enters Assam near Sadia and meets with rivers Dibang and Lohit, forming river ‘Brahmaputra’. It enters Bangladesh near Dhubri, and flows into the Bay of Bengal as river Yamuna. There are numerous point bars in river Brahmaputra, of which the Majuli island is the largest river bar of the world. The main right bank tributaries are Buri Dihang, Disang, Kapili and Dhansiri. The main left bank tributaries are Subansiri, Kameng, Manas, Sankosh and Tista.

C. River Indus: The river Indus originates from the ‘Sengge Khabab’ waterfalls, north of Manas Sarovar near Tibet. It enters Jammu & Kashmir and flows for 709km. Then it flows through Pakistan before meeting the Arabain Sea. Only the mountainous phase of the river Indus lies in India. The main tributaries are-Jhelum, Chenab, Ravi, Beas and Sutlej, on the left bank. These rivers are also known as the ‘Panchnad’ of Punjab.

D. Other Rivers :

• Inland Rivers : Some rivers rise in the mountains but do not meet the sea. Instead, they flow into some lakes or waterbodies within the land surface. Such rivers are called Inland rivers. The only such river in India is river Luni of Rajasthan, which rises from the Aravalli range near Ajmer and ends in the marshlands of Rann of Kutch.
• West-flowing Rivers : Rivers Sabarmati and Mahi rise from the Aravalli and Vindhya mountains and flow into the Gulf of Kambey.
• East-flowing Rivers : Subarnarekha, Brahmani, Baitarani, etc. are some east-flowing rivers of North India.

2. The South Indian Rivers:
The South-Indian rivers are rainfed and older than the northern rivers. Most of them rise from the Western Ghats and the highlands of the Peninsula. The main rivers are discussed in the next page :

A. River Godavari (1,465km) : River Godavari rises from the Tryambak peak of the Western Ghats, flows across the Peninsula and meets the Bay of Bengal through Andhra Pradesh after dividing itself into rivers Gautami, Bashistha etc. It is the longest river of South India and had been dubbed as the ‘Dakshina Ganga’the south Ganges river of India.

B. River Krishna (1,290 km): This rises from Mahabaleshwar peak of Western Ghats in Maharashtra, then flows through Karnataka and Andhra Pradesh and meets the Bay of Bengal.

C. River Kaveri (805 km) : This rises from the Brahmagiri peak of the Westem Ghats in Karnataka and flows into the Bay of Bengal through Tamil Nadu. The main tributaries are-Himavati, Bedamati, Amaravati, Lakshmantirtha, Simsa, Bhavani, etc.

D. Other Important Rivers : Amongst the numerous South-Indian rivers, the other main rivers are-Mahanadi, Tungavadra, Pennar, etc.

Climate Of India

a. Introduction : India being a vast country, experiences a variety of climatic conditions in different regions. But the general climate that can be seen here is ‘Tropical Monsoon Climate’.

b. The controlling factors of climate of India :

1. Location : India extends from 8°-37° N latitudes. This vast latitudinal extent causes vast difference in temperature in the north and south. The region north of the Tropic of Cancer (23{1/2N) is much cooler than the south.

2. Relief: The presence of the Himalayas control the climate of India to a large extent. It stops the chilled Siberian winds from entering and the moist monsoon winds from escaping from India. Thus it controls rainfall and temperature of India. The Western and Eastern Ghats also help in causing rainfall from the monsoon winds. The eastern slopes of Western Ghats is a rain shadow area. While the Coromondal coast gets rainfall twice a year.

3. Altitude : The higher mountainous regions are much cooler than the plains. Hence, places standing on the same latitude but different altitudes will have different temperatures.

4. Distance from sea : The regions near the sea experience moderate or maritime climate. The regions far away from the sea experience extreme or continental climate.

5. Soil : Different soils have different water holding capacities. The dry soils get heated very quickly making the region very hot. The wet soils can retain heat and keep the regions comparatively cooler.

6. Wind: The predominant winds that blow over India are the south-west monsoon winds in summer and north-east monsoon winds in winter, which makes India a ‘Tropical Monsoon Climate Country.’

7. Air current and air pressure : The location of India on the earth gives if the influence of Tropical winds which are blowing towards the Equator from the right, as guided by the Coriolis Force. The pressure conditions near the equator is low and that in the Tropical zone is high.

This controls the upward or downward movement of air, i.e., air current. The sub-tropical region experiences a ‘jet stream’ (27° 30°N) known as the sub-tropical westerly jet stream, which blows in the southern region of the Himalayas. This influences India’s climate to a great extent.

Influcence of the Himalayas on the Indian Climate:

• Protection from severe cold polar winds.
• Orographic or relief rainfall from the monsoon winds.
• Lower temperature on higher altitudes.
• Source of rivers, hence influence on the climate by controlling temperature.

Characteristics of Indian Climate

• Nature : India being located in the tropical region, and almost all parts enjoying the influence of the monsoon winds, the climate of India is called ‘Tropical Monsoon Climate.’
• Season change: Mainly 4 seasons are seen in India, which come in cyclic order throughout the year. Namely summer, monsoon (rainy), autumn and winter.
• Humidity : The summer is humid and the winter is dry in India. For this, India is also called ‘The country of endless season.’
• Duration of seasons: The summer lasts for much more time than the winter.
• Temperature : The summer temperature increases from north-east to north-west of the country and in winter it recedes in just the opposite manner.
• Rainfall : About 80% of rainfall in India occurs due to the south-west monsoons.
• Dryness : The north-east monsoons blow from over the land, hence the winter is dry.
• Wind : The south-west monsoon and the north-east monsoon winds blow in just opposite directions.
• Winter rain : The combined effect of ‘western disturbances’ and low pressure in the Bay of Bengal may cause rainfall in some places in winter.
• Snow fall: During winter, the peaks of the Himalayan range and some places in the north experience snowfall.
• Loo : A hot local wind ‘loo’ blows over western and central India during the summer.
• Highest rainfall : The highest rainfall in the world occurs in Mawsyinram near Cherrapunjui in Meghalaya (1,350cm)
• Flood and drought : Both flood and drought are common due to whimsical rainfall in India.

Rain Shadow : The main rain shadow area of India is-

• The eastern slopes of the Western Ghats
• Shillong and the nearby places in Meghalaya, (c) and (d) Nature of the Monsoon winds at India.

The Monsoon winds are a greater representation of the land breeze and sea breeze. It comes from the word ‘Mausin’ which means ‘seasons’ in Arabic. The term ‘monsoon’ was first used by Edumund Halley in 1686. The winds can be divided into two categories – the hot, wet-south-west monsoon winds of the summer, and the cold, dry, north east monsoon winds of the winter.

A. The south-west monsoon winds
The Tropic of Cancer gets the sun’s direct rays on 21st June. Following this period, a powerful low pressure cell starts developing over the north-western parts of India. This low pressure gradually attracts the monsoon winds from over the Indian ocean. The arrival of monsoon with thunderstorms and torrential showers is also called ‘the Burst of Monsoon’. The two branches of the south-west monsoon are:

• The Arabian Sea branch
• The Bay of Bengal Branch.

The Arabian sea branch : This branch can be further sub-divided into three sub branches :

• The first branch hits with the western slope of the Western Ghats and provide profuse rainfall (300-500 cm). The eastern slope falls under the rain shadow area.
• The second branch enters Maharashtra but fails to provide enough rainfall (only 60-70 cm ) due to absence of highlands.
• The third branch blows parallelly to the Aravalli range and provides very little rainfall (25-50 cm).

The Bay of Bengal branch : This branch is sub-divided into 2 subbranches.

• The first branch crosses Bangladesh and enters India from the north-east. Obstructed by the Garo, Khasi and Jayantiya hills of Meghalaya, it provides torrential rainfall in this region. Mawsynram near Cherrapunji receives the highest rainfall in the world (1,350cm). The Shillong region lies in the rain shadow area.
• The second branches hits with the Himalayas in the north-eastern part and movies ward gradually. As it moves westward, amount of rainfall goes on decreasing (Kolkata 200 cm), Patna-125cm, Allahabad- 75 cm, Delhi- 60 cm). Rajasthan in the extreme west receives only 25 cm. of rainfall.

B. The north-east monsoon winds :

After 23rd September, heat gradually starts reducing in India. The low pressure trough created during the summer slowly turns into a high pressure trough. Hence, the extra wind starts blowing back from there in the same path as the on going south-west monsoons.

These winds are also called ‘Retreating monsoons.’ As these winds generate and blow over land surface, they are dry. Some parts of the wind blow over the Bay of Bengal and re-enter the land surface, providing rainfall to the Tamil Nadu or Coromondal Coast before finally leaving the land.

c. Seasons of India : The unique characteristic of tropical monsoon climate is ‘seasonal variations’ of climatic conditions. The main seasons identified in India are :

• Summer
• Monsoon
• Autumn
• Winter.

Summer (March to May) : After 21st March, the sun gradually moves northwards towards the Tropic of Cancer. The temperature of India increases rapidly during this time, creating low pressure cells on the land surface. The average temperature in March lies between 30°-35°C.

In April it increases to 38° C except the Himalayan region. In May, the average temperature of Jaisalmer (Rajasthan) is 44° C  Delhi and Kolkata is  38° C  A low pressure trough extends from Rajasthan to Chotanagpur during this time, causing some local winds like-Loo, Andhi, Norwestors, etc.

2. Monsoon (June to September) : On 21st June, the sun shines vertically on the Tropic of Cancer. During this time the whole of northern India gets very hot. The low pressure trough that is formed in the north-western region becomes very strong, attracting the monsoon winds into the land.

The south-east trade winds cross the equator and enter India blowing as the south-west monsoon winds, causing heavy rainfall. We have discussed this earlier. Kerala gets the monsoon rains first amongst the states of India.

3. Autumn (October to November): This is the time of retreat of the monsoon winds. The sun gradually moves towards the Tropic of Capricorn, reducing the average temperature of the Indian landmass. The rainy season or monsoon comes to an end. The low pressure cell is now generated over the oceans, which help the north-east monsoon winds to blow out of the country. Some cyclonic winds are created when the hot winds meet the moist winds over the Bay of Bengal.

4. Winter (December to February) : During this time the sun gives its direct rays to the southern hemisphere. Hence, average temperature of whole India reduces remarkably. High pressure prevails over land, especially the north-western region. This helps to drive the north-east monsoon winds to blow away from the land. These are dry winds and don’t cause any rainfall. But a portion of the wind collects moisture from the Bay of Bengal and re-enters the land to provide rainfall to Tamil Nadu Coast.

d. Rainfall Distribution: Parts of western coast and northeastern India receive over about 400 cm. of rainfall annually. However, it is less than 60cm. in western Rajasthan and adjoining parts of Gujarat, Haryana and Punjab. Rainfall is equally low in the interior of the Deccan plateau and east of the Sahyadris.

Why do these regions receive low rainfall ? A third area of low precipitation is around Leh in Jammu and Kashmir. The rest of the country receives moderate rainfall. Snowfall is restricted to the Himalayan region.

Owing to the nature of monsoon the annual rainfall is highly variable from year to year. Variability is high in the regions of low rainfall such as parts of Rajasthan, Gujarat and the leeward side of the Western Ghat. As such while areas of high rainfall are liable to be affected by floods, areas of low rainfall are drought-prone.

Soils Of India

Introduction : The material on the earth surface within which horizons or layers have developed is known as soil. It is made up of solid, liquid and gaseous substances.

Classification of Indian Soils : The Indian Council of Agricultural Research [CAR] has divided the soils of the country into 27 types according to their colour, texture, mineral and retentive capacity of moisture. But for the convenience of the discussion, the types are classified here into following 7 categories.

1. Alluvial Soil :

a. Areas : In north India the soil of this type occurs in the large plains formed by the river system of the Ganga, Indus and Brahmaputra. In Peninsular India it occurs in plains of Gujarat and deltas of Mahanadi, Godavari, Krishna and Kaveri rivers. It covers nearly 45% of the total land of the country.

b. Features :

• The soil is fine-grained and is formed of sediments brought down by rivers,
• This soil is rich in nutrients like calcium phosphoric acid, lime and other substances,
• It is rich in humus and potash,
• It is very fertile and very suitable for cultivation.

c. Types: This alluvial soil is of two types,

• Bhangar: The alluvium that is comparatively old and coarse is a little less fertile. It is often found in the upper sides of the valleys of rivers etc., where the silt is coarse and pebbly. It is called Bangar. It is dry, porous and sandy. It contains kankar nodules in the sub-soil,
• Khadar: Relatively new alluvium is found in the flood plains and deltas. It is locally known as khadar and is most fertile. It is relatively compact, fine and moist. It is more sandy and is free from kankar nodules in the sub-soil.

d. Agricultural value : The alluvial soil is regarded as the best soil of India for its high agricultural value. Crops like rice, jute, vegetables and sugar-cane grow very well in this type of soil.

2. Black Soil :
a. Areas: These soils are found in the Deccan Plateau, comprising Maharastra Plateau, Malwa Plateau, Telengana-Raylaseema region of Andhra Pradesh, northern parts of Karnataka, Gujarat and in some parts of Tamil Nadu.

b. Features:

• It is black in colour,
• Derived from the Latin word ‘Ragurgitare’ it is also popularly known as ‘Regur’.
• It is clayey and has capacity to retain water,
• It is sticky and hard,
• Originating from the basaltic rocks of lava plateaus, it is finely grained and contains iron, calcium carbonate, potash and lime but is poor in phosphates and organic matters.

c. Agricultural value : These soils are most suitable for cotton cultivation. Hence they are known as black cotton soils. They are also suitable for sugarcane, wheat and groundnut.

3. Red Soil : Areas : Red Soil is found in the states of Kerala,
TamilNadu, Karnataka, Andhra Pradesh, Orissa and Jharkhand.

Features :

• It develops on crystalline igneous rocks in areas of poor rainfall
• It is reddish in colour due to its high iron content,
• It is more sandy and less clayey.

Crops : Rice, wheat, sugarcane, cotton and pulses are cultivated on it.

4. Laterite Soil : Areas: This soil is found in the hilly areas of the Western Ghats, Chhotanagpur Plateau and the hills of Meghalaya.

b Features :

• It develops as a result of leaching in areas of heavy rain. Hence it is found capping the tops of hills and hill-slopes,
• It is coarse  in texture and not fertile since its nutrients are washed away
• The word  ‘laterite’ comes from a latin word ‘Later’ which means brick; in fact, these soil looks like dust of red bricks
• It cannot retain moisture,

Crops : It is not suitable for agriculture. Cashew plants, tapioca, cotton, wheat etc. are grown in this soil.

5. Desert Soil :
Areas : It is found in western Rajasthan, northern Gujarat and southern Punjab.

Features :

• It is coarse in texture,
• It is characterised by sandy texture,
• It contains 90% to 95% sand and 5% to 7% clay,
• It contains high percentage of soluble salts and have high PH value
• It is poor in organic matter,
• It is not fertile

Crops : Wheat, cotton, grapes, oranges etc. are grown.

6. Saline Soil :  Areas : This soil is found along the east and west coast of India,

Features :

• This soil is black, heavy and highly acidic and contain 10% to 40 % of the organic matter
• It is more sandy than clayey,
• It is saline in nature due to oceanic influence.

Crops : Rice and coconut are grown abundantly in this soil.

7. Mountain Soil : Areas : It is found in the Himalayan region.

Features :

• This soil varies in different regions according to the altitude,
• It is rich in iron but deficient in lime,
• It is rich in humus and is acidic.
• The remains of the leaves of trees enrich the soil with humus.

Crops : Tea, fruit, rice etc. are grown.

Importance of Soils : Many human and economic activities depend upon soils. All our food comes directly or indirectly from soils. Livestock farming depends upon raising of grass on different soils. Soils have affected the march of civilisations. Soils are mainting the humidity in environment. Ancient civilisations developed in fertile river valleys. Fertile soils attract human settlements. Density of population depends upon soil fertility and productivity.

Soil Erosion : The removal of top soil by running water, wind, etc is called soil erosion. The destructon of the soil in an area is known as soil erosion. Soil erosion in the cultivated lands leads to lower yield of crops because the producivity of the soil declines.

Soil conservation : Soil is a non renewable resource. It is difficult to replace the soil from areas where it has been eroded. Therefore, it is necessary to protect the soil from erosion. The following measures may be adopted for conservation of soil :

• Contour ploughing method tends to check soil erosion on the hill slopes by preventing the flow of water down the slope.
• Cattle grazing should be restricted.
• The extraction of minerals from great depths beneath the soils should be banned.
• Tree felling should be banned.
• Step cultivation should be practiced on the hill slopes.
• Saplings in large numbers should be planned.
• Roads, buildings and hours should not be constructed along the slopes.

Natural Vegetation

Introduction : Natural vegetation refers to the vegetation that grows with the help of soil, water, sunlight and other physical environment, without the interference of man. In India, about 20.55% land is under forest cover.

Types of vegetation : Natural vegetation has a close relation with climate and relief, hence differs from place to place. They can be categorised as follows :

Evergreen Rain
Forests:  Climate These forests are found in areas with an annual rainfall of 200 to 300 cm or more. They need high humidity and even temperatures (25° to 27°C) through out the year.

Characteristics:

• The trees in these evergreen forests are very dense,
• These contain numerous species of high commercial value, because of the timber being hard, durable and fine grained.
• Trees are tall,
• The ground remains wet throughout the year
• This dense forest with trees and thick undergrowth makes communication difficult. Hence these are difficult to exploit for commercial purposes.

Trees: The main trees are rosewood, poon, aini, telsur, champa, gurjan, toon, chaplas, boga, poma, sisoo, iron wood, mango etc.

Areas: These are found on the windward side of the Western Ghats and in the hills of N. E. India, West Bengal and Orissa.

2. Tropical Deciduous Forests : They can be divided into 2 parts :
A. Wet Deciduous or Monsoon Type of Forests :  Climate : These are found in regions with an annual rainfall of 100 to 200 cm, the mean annual temperature of 26° C to 27° and humidity percentage ranging between 60 and 80. These are monsoon forest type :

Characteristics :

• The trees are deciduous, shedding their leaves in the dry season and not growing new ones until the rains,
• Majority of the trees are broad-leaved and yield valuable hardwoods.

Trees: The main trees are teak, sal. sandal wood, deodar, bluegum, ebony, sisam, jackfruit, mahua, palash, arjun, khair and bamboo.

Areas : These are mostly found on the lower slope of the Himalayas, Assam, West Bengal, Bihar, Jharkhand, Orissa. Madhya Pradesh, Maharastra, Karnataka and the adjoining regions.

B. Dry Deciduous Forests or Scrubs : Climate: These forests are mostly found in areas having a mean annual temperature of 23° to 27° C, an annual rainfall between 50 to 100cm. and humidity ranging between 51 to 58 %.

Characteristics:

• These forests consist of stunted trees and bushes which are widely scattered.
• They fade away into scrubs and thorny bushes, typical of the desert region.
• Trees are only 6 to 10m high
• They have long roots which enable them to obtain water from deep underground.

C. Trees : Babul, Kikar and wild palms are common trees. Species of acacia are also found.

D. Areas : These are found in areas of central Deccan Plateau, south-east of Rajasthan, Punjab, Haryana and parts of Uttar Pradesh and Madhya Pradesh.

3. Semi-deserts and deserts vegetation :  Climate: These forests occur in arid areas with a yearly rainfall of less than 50cm. a year.

Characteristics:

• The type of vegetation grown here consists of thorny shrubs like cactus, prickly pear and other plants which are adapted to survive in a region of low rainfall. These are called xerophytic plants and have adaptations to withstand drought
• Short coarse grasses grow here and there,

Trees : Babul, Acacia, Senegal, Prosopis, Spicigera and Juliflora grow very well.

Areas : These are mostly found in Rajasthan and parts of Gujarat, Punjab and Karnataka.

4. Tidal Forests : These forests are also known as Mangrove Forests or Littoral Forests [‘littoral’ meaning ‘on a shore’]. In the delta of the Ganga, they are known as the Sunderbans, because of the Sundari trees found there.

Environment : On the coastal tide washed coast where mud and silt have accumulated, dense mangrove forests flourish. These forests are impenetrable due to their dense growth and the tangle of climbers on them. The trunks of the trees are supported by a number of stilt-like roots, which are submerged under water at high tide, presenting a scene of a flooded forest.

At low tide, the stilt-roots supporting the trunk of the tree above, appear to be emerging out of the soft mud. Such a mass of root-system has been provided by nature to fix the tree in the mud banks.

Trees : Sundari, keora, goran, gewa, amur, bhara, agar, bani, hogla, golpata, gilepata etc. are important trees of tidal forests.

Areas : In India mangroves cover a total area of 6,740sq. km. which is about 7% of the world’s total mangrove. Mangrove forests are found in the Sundarbans (W.B.), the Mahanadi deltas, the Godavari deltas, the Krishna deltas, the Kaveri deltas and along the coasts of the Andaman Islands.

5. Mountain Forests : Mountain forests vary considerably according to altitude with varying rainfall and temperature along the slopes of mountain :

• On the foothills of the Himalayas upto a height of 1500 metres, evergreen trees such as sal, teak, bamboo and cane grow abundantly,
• On higher slope between 1500m. to 3,500m, temperate conifer trees such as pine, fir, oak, maple, deodar, laurel, spruce and ceder grow. At the higher altitude of the Himalayas, rhododendrons and junipers are found. Beyond these vegetation belts, alpine grasslands appear upto snowfield.

Uses of forests : Forests not only help to maintain the ecological balance of the earth, but they have also multiple uses:

• Forests are the houses of numerous species of plants, animals, insects, birds, etc.
• The trees have different uses, e.g. Hardwood trees of evergreen.

Forest

Importance of forest and its influence on mankind : Forests are a valuable resource; like a river system, it is a multiple resource. Forests provide mankind with a number of products. Forests have greatly influenced human activities. Modern civilisation depends more and more on forests. Following are the direct and indirect advantages of forests :

• Forests provide many things to meet our food requirements like wild fruits, nuts, berries, etc. Many tribes are dependent on gathering of these products in forests.
• Forests are a source of timber for house-building, furniture making, ship building, etc.
• Forests supply about 40% of fuel of the world. Wood has been the major source of fuel in houses, smelting industries and running locomotives.
• Soft woods supply raw materials for wood pulp, paper, rayon industries.
• Many products like rubber, pitch, gum, tanning materials, cork, camphor, fir, herbs, etc. are gathered from forests.
• Forests provide plywood and firewood and also wood for packing purposes.

Forest Resources of India :

About 19.39% of the total land in India is under forests. The total forests area in India is about 63.73 milion hectares. Forests play and important role in the country’s economy. They are useful in maney ways. They provide wood, fur, fuel and timber. They provide grazing ground for cattle. They are the home of wild animals.

They are a source of employment to a large number of people. They provide structural timber and wood for making furniture and pulp, match wood, wood for charcoal, gum, resins, canes and fibres. Besides these there are many other forest products such as leaves, fruits, tandyes, medicinal herbs, bee-wax, honey, turpentine oil and lac.

Problems of Forest and their solution :

Theoughtless and rapid exploitation of our forest resources has damaged our ecosystem beyond repair. On an average, India has been losing 1.3 million hectares of forest land every year. This is an alarming situation indeed. It is, therefore, necessary for us to consume the forest resources and increase the forest areas.

To presence the forest the Govt. of India has taken up a series of programmes iun support of the states: The forests are declared as Resemed Forests. A beautifull programme of ‘Van Mahotsav’ has been chalked out by the government. 21st March is observed as “world Forest Day” every year. The Forest research Institute has been set up in 1987 at Dehra Dun. A scheme of ‘social forestry’ has been taken in the in habited areas. It is a plan for afferestation as well as conservation of forest.

Some Essential Herbs:

Plants which have medicinal uses are called Herbal or Medicinal plans. These are used in India since ancient days. The method of treatment with different herbsis known as Ayurveda Medicine. A list of some important useful herbs is given below.

Name of plant	Parts used	Medicinal use	Places where found
1. Basak	Leaf	1. Cures cold and cough, 2. Skin disease.	West Bengal, Assam, Tripura etc.
2. Neem	Oil from seeds leaves	Good for liver, skin and teeth	West Bengal and other states.
3. Cinchona	Bark	Source of quinine, cures malaria, fever and pain	Mongpu in Darjeeling district of W.B. is famous for cinchona cultivation.
4. Basil	Leaf	Provides relief in asthama, cough and cold and indigestion, Good for heart.	All status.
5. Sarpagandha	Root	Reduces high blood pressure, insomnia, hypertension	Humid areas in Western Ghat.
6. Chirata	Soft stem	cures liver stomach diseases	Meghalaya and the Himalayan moun­ tainous area.
7. Kalmegh	Whole plant	works as antibiotic, Fever weaknes, release of gas, liver function.	West Bengal, N. En status, South Indi.

Wildlife of India

Generally all the lives other than domesticated or cultivated ones which live freely and adapt in natural habitats are known as wild life. The wildlife in our country is our national heritage and asset. India has a rich and varied wild life. Various Kinds of wild animals and birds are found in the Indian forests. Some of the important animals are lions, tigers, leopards, elephants, bears and rhinoceros etc. Lions of the Gir forests in Gujarat are well known all over the world.

In Asia, lions are found only in the Gir Forest. Tiger, the largest of the cat family, is found only in Asia. There are two types of tigers-the Siberean tiger and the Bengal tiger. The Bengal tiger is now found only in India. India is the home of several well known variety of wild life which includes-

• The Royal Bengal Tiger and giant crocodiles at Sunderbansareas in Weset Bengal.
• Indian one-horned rhinoes at Kaziranga National Park in Assam.
• Black Panther and Indian elephant Anshi National Park in Karnatka.
• White Tiger at Bandhavgarh National Park, Madhya Pradesh.
• Rede Panda, Wild cat, Cheetah and monkeys at Himalayan mountainous region such as meghalaya and other north-eastern mountainous states.
• Sambar, Barking deer, Gaur, Jungle cat, wild boar at Simlipal National Park in Odissa.We have at present about 500 species of wild animals. We also have a large variety of birds (about 1300 species). Among such birds is the peacock which has been declared as our national bird. Our national animal tiger.

Reserved Forest : A reserve forest or a reserved forest is a specific term for designating forests and other natual area, which enjoy judicial and or constitutional protection under the legal systems of many countries. In reserved forests hunting, grazing and other activities are prohibited, e.g. Kodarma Reserved Forest.

Difference between Reserved Forests and Protected Forests.

Reserved Forests	Protected Forests
1. These forests are under the direct supervision of the government and no public entry is allowed for collection of imber or grazing of cattle.	1. These forests are looked after by the government, but the local people are allowed to collect fuel-wood/timber and graze their cattle without causing serious damage to the forests.
2. About 53 percent of the total forest area falls in this category.	2. These forests occupy about 29 percent of the total forest area of the country.

Protected Forest : A protected forest is a forest with some amount or legal or constitutional protection, or where the habitat and resident species are legally accorded protection from further depletion.

Unclaissifed Forests : Forests are those in which there is no restriction on the cutting of trees and grazing of cattle. About 18 per cent of the total forest area of the country falls under this category.

• National Park : It is a reserved area both for preserving natural vegetation, natural beauty and wildlife, e.g. Kaziranga National Park.
• Sanctuary : A sanctuary is a reserved area meant for the preservation and development of endangered species.

Conservation of Wildlife : In order to save wildlife the Indian Board of Wildlife has taken several steps, to prevent the extinction of birds and animals.

• Setting up of sancturies and parks. At present we have 83 National Parks and 490 sancturies besides 21 tiger reserves.
• Appointment of observers for wildlife.
• Creation of buffer belts around the sancturies where shooting of animals is prohibited.
• Prohibition of netting of birds and animals and their sale.
• Fixation of annual limits regarding export and import of animal skins and other products.
• Celebration of wildlife week.
• Tigers are preserved in the Corbett Park. here is a park for rhinoceroses in Assam.
• There is a large bird sanctuary at Bhartpur.
• 24200 logical parks have been set up in different parts to preserve wildlife.
• The wildlife Protection Act was constituted in 1972.
• Every year we observe wildlife week in the first week in the first week of October, to creat awareness of conserving the habitats of the animal Kingdom.

Agriculture Of India

Definition of Agriculture : The act of cultivating crops, rearing animals along with fisheries and forestry is termed as “agriculture”. India is essentially an agricultural country or agro-based country. About 65% people of India are involved with agriculture in some form or other.

The large array of crops grown in our country may be grouped under two principal categories namely Food and Cash. The important crops grown are outlined in the following chart.

The method of cultivation hilly areas by cultivation in hilly areas by making steps on slopes to prevent soil erosion is called steps cultivation.

Green Revolution : There was a big change in Indian agriculture is late 1960s. Agricultural production increased manifold by using high yielding seeds, fertilizers, irrigation and improved technology. This was called Green Revolution.

Cropping Seasons : The dominent cropping seasons of our country are Kharit and Rabi.

A Kharif Crops : Kharif season has monsoon or summer crops. They are associated with south west Monsoon. The crops, which grow during monsson or Kharif season are known as Kharif crops. These crops are sown in the rainy season. Kharif season begins with the ground preparation is April-May.

The seeds are sown after the onset of southwest monsoon (June-July) and harvested in autumn (November). The Kharif crops are rice, millets, cotton, Jute, sugar cane, sesamum and groundnuts.

A Rabi Crops : The crops, which grow during Rabi season (Novemeber to February)are known as Rabi crops. the Rabi crops are sown in winter and harvested in spring. The ground is prepared by the end of October or the bigining of November and the crops are harvested between Mach and May. The principal rabicrops are what, gram, linsee, rape seed and mustard.

Zaid crops : This is summer cropping season and major said crops are rice, maize, groundnut, Vegetable and fruits line water melon musk melm, Cucumber etc.

Cash crops : The Crops which are grown, harvested and sold for cash rather than for sustenance. In other words, the crops, which earn money, particularly the foreigin and domestic exchange, ae known as cash crops. he principal cash crops in India are Tea, Jute,cotton, sugarcane and coffee.

Plantation Crops : In certain cases, theplantaior, of crops is doneonce and the crop obtained for a number of years. Many such crops are tree crops. The most important examples of plantation crops are tea, coffee and rubber.

A. Foods crops

B. Cash Drop:

Tribes Of India

Introduction : The term tribal is usually applied to the aboriginal population of India not in derogatory sense but as an indication of their being the earliest among the present

inhabitants of this country. Not all of them are in the same stage of culture or speak the same language or are racially homogeneous. India has the largest population of such people (about 84.4 million in the word) who are commonly called tribes. They are also known as adivasis.

They are poorest and perhaps the most backward. They are of mixed origin, varying cultures and very different physiques, colour and appearance. Some of the major tribal groups in India include Gonds, Santhals, Bhils, Khasis, Angamis, Bhutias and Andamanese. Let us now know about some main tribes of India.

Garo : Garo are founded in Garo hills of Meghalaya, like in a society governed by the principles of mother right. Physically, Garos are not very dark. The Garo is essentially an agriculturist. Household utensils and implements are very simple. They consist of cooking pots, larger vessels for brewing liquor, and the pestle and mortar with which paddy is husked or rice cleaned for eating. Among the Garos, the proposal for marriage always comes from the girls side.

She indicates her choice to a male member in the family, who then pursues the matter. Among some of the groups, it is customery to “capture” the boy and bring him to the girl.

Khasis : Khasis are found in Khasi, Jaintia hills in Meghalaya. They cultivate the hill sides and terrace cultivation is the rule butit is done only in the flat valleys. They speak Khasi language. They follow chrustianity. Music plays an important part in their life.

Gonds : The Gonds are amongst the most civilized and advanced aboriginal tribes of India. The present habitat is confined in the Satpura plateau, Baster, a portion of Nagpur plateau and valley of river Narmada in Southern India. The land of Gonds is known as Gondwana.

They speakthe Indo-Aryan language Bhili. Gond village is seen along the river banks. Besides agriculture the Gonds also practise hunting. Their main hunting arms are the arrow and the bow.The arrows are generally impregnated with deadly poison.

Bhils: They are mainly confined to Madhya Padesh, Khandesh, Rajasthan, Gujarat and some districts of Uttar Pradesh. They are popularly known as the bow men of Rajasthan. They are the largest tribe of the whole of South Asia. The Bhils are very much violent and warlike. They also consume intoxciants, especially the local made liquor, which they extract from the Mahua (Bassia Latifolia) trees.

Santhals: Santhals are the third largest tribe in India. They are mostly found in the states of West Bengal, Bihar, Odisha, Jharkhand and Asam. The main occupation of the Santhal is agriculture. Millet and maize are the staple crops of the Santhals. Lumbering, fishing and hunting are the chief sources of our their livelihood. They speak Santhali language. They also speak Bengali, Oriya and Hindi.

Munda : Mundas are the inhabitant of Jharkhand. They are also found in West Bengal Chhattisgarh, Odisha and Bihar. Hunting is the chief occupation of Mundas. Munda generally means the headman of the village.

Chechu : The chenchus of Nallaimalklai and Andha Pradesh (now Telengana) sides of Krishna river are one of the greatest food-gathering tribes. The people living or wild fruits, and tubers etc. also sometime chase wild animals for their flesh. The main hunting arms of them are the arrow and bow. The eke out their livelihood with great difficulty. They worship a number of deities. Some of them also follow Hindu culture and tradition.

Kinnaur : Kinnaure are the tribes of Himachal Pradesh. They speak Kinnauri language. They are mostly engaged in livestock raising.

Todas : They are inhabitant of Nilgiri hills. They speak in Toda and Telegu languages. Their main occupation is cattle rearing.

Bhutia : The habitat of the Bhotia is confined to the northern mountainous regions of Kumaon along Tholi river, above Badrinath and in Almora distric.

Jarawas : Jarawas are the native people of South Andaman and Nicobar

Islands currently, they are inhaviting the south and middle partis of the Andaman islands. According to the 2011 census of India, there are around 200 to 500 Jarawas living here. Jarawas use bows and arrows which they make from iron edges and wooden handles. Jarawa villages have a population of about 25 people on average with 5 to 10 huts. In their culture, huts are called “Chadda” and the residence of the hut are the “Tutime chadda”.

Onge : The onge’s are a negrito tribe residing in little Andaman. According to 1971 census they were 117 in number. While the Onge men go out to the forest for hunting, the women will stay back at home and search the local area for roots and tubers under the soil. They have little interest in cultivation.

Shompen : They reside in the interiors of great Nicobar Island. The main activities of Shompens are hunting, food fathering.

People of India:

Unity in diversity is a famous concept which best fits of India. We can see very clearly here that people of different religious, creeds, castes, languages, cultures, lifestyle, dressing sense, faith in god, rituals of worship, songs, fetivals, dance forms, folk culture, traditions etc. live together with harmony under one roof means on one land of India.

People of different religions Hinduism, Buddhism, Islam, Sikhism, Jainism, Christianity and Parsees live together. People celebrate their festivals like Holi, Diwali, Dosshara, Janmastami, Durga Utsab (Hinduism); Id, Eid-ul-Fitr, Muharram (Islam) Christmass Easters, Good Friday (Christianity); Mahavir Jayanti (Jainism); Buddha Jayanti on Buddha Purnima (Buddhism); Guru Purab (Sikhism) etc. very peace fully without harming other religious people.

We all togetherly observe the National days, with reverence on 15th August-Independence Day, 26th January-Republic Day and on 2nd October – The Birthday of Mahatma Gandhi, the Father of the Nation.

 

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 5 Realms of the Earth: Water-Land-Air offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 5 Question Answer – Realms of the Earth: Water-Land-Air

Objective Type Questions [1 mark each]

Question 1.
Which layer of atmosphere protects us from the harmful ultra-violet rays of the Sun?
Answer:
Ozone layer

Question 2.
What is the upper limit of the atmosphere?
Answer:
Exosphere

Question 3.
What is the percentage of oxygen gas present in the atmosphere?
Answer:
21 %

Question 4.
What name is given to zone of living things?
Answer:
Biosphere

Question 5.
Which hemisphere is called water hemisphere?
Answer:
Southern Hemisphere

Question 6.
Which is the largest ocean?
Answer:
Pacific Ocean

Question 7.
Which is the main source of water on earth?
Answer:
Ocean

Question 8.
What do you mean by Hydrosphere?
Answer:
Sphere of water.

Write short notes on : [2 marks each]

Question 1.
Pangaea.
Answer:
500 million years ago, the world map was not as it is today. There was one huge integrated landmass or mothercontinent called the Pangaea.

Question 2.
Continent.
Answer:
Landmasses of large extent are called the continent. There are seven continents of the earth. These are Asia, Africa, Europe, North America, South America, Australia and Antarctica.

Question 3.
Panthalassa
Answer:
The Pangaea was surrounded by the gigantic water body or Super Ocean called the Panthalassa.

Question 4.
Ozonesphere.
Answer:
This is a zone of ozone gas. It absorbs ultra-violet rays of the Sun. It has high temperature. Due to excessive use of chemicals and carbons, the ozone layer is being depleted.

Question 5.
Why is life possible on the earth?
Answer:
The earth is a unique planet. It has plenty of water. The earth has air. Oxygen and Nitrogen gases support life. All kinds of life depend upon water and air. First life on earth evolved in the water.

Question 6.
Why is the Biosphere important for living organism?
Answer:
Life exists in Biosphere. All the living organisms are interlinked for their survival. It consists of plants and animals. In this sphere of life, lithosphere, atmosphere and hydrosphere meet.

Question 7.
How are oceans useful to us ?
Answer:

• Oceans modify land temperature.
• Oceans are source of water vapour that causes rainfall.
• Oceans are means of transport.

Question 8.
What is isthmus ?
Answer:
An isthmus is a narrow strip of land joining two large landmasses or separating two large water bodies.

Question 9.
What is Gulf ?
Answer:
A deep inlet of the sea almost surrounded by land with a narrow mouth is called a gulf.

Question 10.
What is Bay ?
Answer:
A bay is wide covering indentation in a coastline.

Question 11.
What is strait?
Answer:
A strait is a narrow passage of water that connects two large navigable bodies of water.

Answer the following questions briefly : [2 marks each]

Question 1.
What do you mean by the term global warming ?
Answer:
The burning of fossil fuels (coal, gas, petroleum) the cultivation of soil, large scale industrialisation, rapid means of transport and deforestation has raised the average temperature of the earth by 0.5° C.

Question 2.
Why is the earth considered a unique planet?
Answer:
Our earth is considered a unique planet in the Solar System because this is the only planet where life is possible. The environmental conditions are favourable for the origin of life.

Question 3.
Define environment.
Answer:
surroundings of a place. The environment includes land, water and air and living objects like plants, animals and humAnswer: Both living and non-living objects are dependent on one another. Our environment

Identify the correct answers : [1 Mark each]

Question 1.
The earth comprises
(a) One realm
(b) Two realms
(c) Three realms
(d) Four realms
Answer:
(d) Four realms

Question 2.
The domain of the earth consisting of solid rocks is
(a) The Atmosphere
(b) The Hydrosphere
(c) The Lithosphere
(d) The Biosphere
Answer:
(c) The Lithosphere

Question 3.
The landmasses form about of the earth’s surface.
(a) 20 %
(b) 30 %
(c) 40 %
(d) 50 %
Answer:
(b) 30 %

Question 4.
The smallest continent of the world is
(a) Australia
(b) Antarctica
(c) Europe
(d) South America
Answer:
(a) Australia

Question 5.
Which is the largest continent?
(a) Africa
(b) Asia
(c) Australia
(d) Antarctica
Answer:
(b) Asia

Question 6.
The two most abundant gases in the atomosphere are
(a) Oxygen and Carbondi oxide
(b) Water vapour and Carbon dioxide
(c) Nitrogen and Water vapour
(d) Nitrogen and Oxygen.
Answer:
(d) Nitrogen and Oxygen.

Question 7.
The lowermost layer of atmosphere is the
(a) Stratosphere
(b) Exosphere
(c) Troposphere
(d) Mesosphere.
Answer:
(c) Troposphere

Question 8.
What is the percentage of Nitrogen gas present in atmosphere ?
(a) 18 %
(b) 38 %
(c) 58 %
(d) 78 %
Answer:
(d) 78 %

Question 9.
Atmosperic disturbances are found in
(a) Stratosphere
(b) Mesosphere
(c) Troposphere
(d) Lithosphere
Answer:
(c) Troposphere

Question 10.
Largest ocean is
(a) Atlantic Ocean
(b) Pacific Ocean
(c) Indian Ocean
(d) Arctic Ocean
Answer:
(b) Pacific Ocean

Fill in the blanks with correct words : 1 mark each.

1. The surface of the earth surrounded by a blanket of air is called ____.
Answer:
Atmosphere

2. Heights and depths of the landmasses are measured from the ____.
Answer:
Sea level

3. The big landmasses are called ____.
Answer:
continent

4. _____ is the largest continent.
Answer:
Asia

5. No permanent human settlement is on the continent of ____.
Answer:
Antarctica

6. ____ is the smallest continent.
Answer:
Australia or Oceania

7. The narrow zone of contact between the land, water and air is the ____.
Answer:
Biophere

8. The deepest point on the earth is ____ in the Pacific Ocean.
Answer:
Mariana Trench

9. The sphere of living things is called ____.
Answer:
Biosphere.

If the sentence is true, write ‘T’ and if false write ‘F’ against the following 1 mark each

1. Europe is the smallest continent.
Answer:
False

2. Oceans cover about 50 % of the earth’s surface.
Answer:
False

3. Nitrogen is the most abundant gas in the atmosphere.
Answer:
True

4. Africa is the second largest continent.
Answer:
True

5. The combined landmass of Asia and Europe is called Eurasia.
Answer:
True

6. The Arctic Ocean lies to the south.
Answer:
False

7. The Arctic Ocean in the North Polar Region is the smallest ocean.
Answer:
True

Realms of the Earth: Water-Land-Air Class 6 WBBSE Notes

Unique Planet: Our Earth is considered a unique planet in the Solar System because this is the only planet where life is possible. The environmental conditions are favourable for the origin of life.
Lithosphere: The solid layer of the earth’s surface is called lithosphere.
Hydrosphere: The surface of the earth that consists of water is known as Hydrosphere.
Atmosphere : The surface of the earth surrounded by a blanket of air is called the atmosphere.
Biosphere : The narrow zone of contact between atmosphere, hydrosphere and lithosphere results in the life which is called the Biosphere.

Introduction :

In this chapter you will study about the realms of the Earth, that is, the liquid hydrosphere (water), the solid lithosphere (land) and the gaseous atmosphere (air).

This will help to understand how the three spheres have together given rise to the Biosphere-the realms of living organisms and made the Earth a unique planet. Earth is the only planet of the solar system that supports life.

Our environment consists of these four realms or parts. The surface of the land consists of rocks and soils. This part of the environment is called the Lithosphere, meaning a layer of rocks. You know that oceans cover much larger area of the earth’s surface than landmasses. Water also occurs on the land and in the atmosphere as water vapour. This realm of water is called the Hydrosphere. There is an envelope of air around the Earth. This is called the Atmosphere. All forms of life occur in the narrow zones of containing various forms of life is called Biosphere. Though there are four realms in our environment, they are all interdependent on one another.

hydrosphere : Realm of water: The earth is commonly known as the blue planet. More than 71 per cent of its is covered with water and 29 per cent is covered with land. Hydrosphere consists of water in all its forms. The water cycle describes the continuous movement of water on, above and below the surface of the Earth. Water goes through changes of state and is converted to cloud, rain, ice or snow as it travels constantly from the air to the surface of the earth and back. This cyclic movement of water through the phases of nature is called the water cycle or the Hydrological cycle. As running water in oceans and rivers and in lakes, ice in glaciers, underground water and the water vapour in atmosphere, all comprise the hydrosphere.

More than 97 % of the Earth’s water is found in the oceans and is too salty for human use. A large portion of the rest of the water is in the form of ice sheets and glaciers or under the ground and a very small percentage is available as fresh water for human use. Hence, despite being a ‘blue planet’ we face a shortage of water!! Hydrosphere consists of oceans, seas, bays, gulfs and lakes.

Oceans : The oceans have a greater extent of water in the southern hemisphere than in the northern hemisphere. There are five oceans. These are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Arctic Ocean and the Antarctic Ocean.

The Pacific Ocean: It is the deepest ocean and the largest ocean. It covers nearly one-third of the Earth’s surface. In fact, it is so big that all the continents could easily fit into it.

The explorer Ferdinand Magellan named the ocean ‘Pacific’ meaning calm or tranquil. The International Date Line passes through the Pacific Ocean. The deepest part of the earth, the Mariana Trench, lies under this ocean. This ocean is bounded on the west by Asia and Australia and on the east by North and South Americas.

The Atlantic Ocean : It is the second largest ocean, about half the size of the Pacific Ocean and it is ‘S ‘ shaped. It is flanked by the North and South America on the Western side, and Europe and Africa on the eastern side. Some of the world’s best seaports (e.g., London, New York, Montreal) are along the Atlantic coast.

The Indian Ocean : The Indian Ocean is the only ocean named after a country. It is bordered by Africa on the west, Asia on the north and Australia in the east.

The Arctic Ocean : It is the smallest ocean and lies within the Arctic Circle. It extends into the Atlantic Ocean and the Bering Strait connects it with the Pacific Ocean.

Seas : The world’s largest seas include the South China Sea, the Caribbean Sea, the Mediterranean Sea and the Bering Sea. The Earth appears bright, blue from the space as three fourths of its surface is covered with water. This is why Earth is called the ‘Blue planet’. Around 3.5 billion years ago the first life on Earth was originated in water. 97 % of all the water on earth is in the oceans. The remaining 3 % is distributed in rivers, lakes, glaciers and underground water reserves.

Lithosphere : Realm of Earth consisting of rocks.

The word ‘Lithos’ means ‘stone’. The solid portion of the earth on which we live is called the Lithosphere. It comprises the rocks of the earth’s crust and the thin layers of soil that contain nutrient elements which sustain organisms.

There are two main divisions of the Earth’s surface. The large landmasses are called the continents and the huge water bodies are known as the ocean basins. All oceans of the world are connected with one another. Are all the landmasses connected with one another?

The level of seawater remains the same everywhere. Elevation of land is measured from the level of the sea, which is taken as zero. The highest mountain peak Mt. Everest is 8,848 metres above the sea level. The greatest depth of 11,022 metres is recorded at Mariana Trench in the Pacific Ocean. Could you imagine that depth of sea is much more than the highest point?

Continents : There are seven major continents. These are-Asia, Africa, North America, South America, Europe, Australia and Antarctica. All these continents are separated by large water bodies. Look at the world map and notice that the greater part of the landmass lies in the Northern Hemisphere.

Asia: It is the largest continent. It lies in the Eastern Hemisphere and covers about one third of the total land area of the earth. This continent is separated from Europe by the Ural mountains on the west. The Tropic of cancer passes through this continent. The combined landmass of Europe and Asia is known as Eurasia [Europe + Asia].

Asia is separated from Africa by Suez Canal.

Africa : It is the second largest continent after Asia. A large part of this continent lies in the Northern Hemisphere. The equator or 0° latitude passes through the middle of the continent. It is the only continent through which the Tropic of cancer (23 1/2° N) the Equator (0°) and the Tropic of capricorn (23 1/2° S) pass.

The world’s largest hot desert, the Sahara is located in this continent. It is bound on all sides by seas and oceans. Look at the map of world. The world’s longest river Nile, flows through Africa. Notice where Equator, the Tropic of cancer and the Tropic of capricorn pass in the map of Africa.

North America : It is the third largest continent of the world. It is completely lies in the Northern and Western Hemisphere. North America is linked to South America by a narrow strip of land known as the Isthmus of Panama. The continent is surrounded by three oceans namely the Pacific Ocean, the Atlantic Ocean and the Arctic Ocean.

South America : Most part of South America lies in the Southern Hemisphere. The World’s longest mountain range, the Andes, runs through its length from north to south. South America is the home of the world’s largest river, the Amazon River. Can you name the two oceans that surround it on the east and the west?

Europe : It is the sixth largest continent. This continent lies to the west of Asia and it is much smaller than Asia. It is bound by water bodies on three sides and the Arctic circle passes through this continent.
Australia : It lies entirely in the Southern Hemisphere. It is the smallest continent and is often called the “Island continent”, as it is surrounded by water.

Antarctica : It is entirely in the Southern Hemisphere. It is frozen land found around the south pole. It contains 75 % of the ice in the world. It is estimated that the ice is about 4 km thick.

Hence, Antarctica is called the “Frozen Continent”. There are no permanent human settlements. Many countries have research stations in Antarctica. India also has research stations in Antarctica. These are named as Maitri and Dakshin Gangotri.

Continental Drift : 500 million years ago, the world map was not as it is today. There was one huge integrated landmass or mother-continent called the Pangaea. It was surrounded by the gigantic water body or super ocean called the Panthalassa. The Pangaea started breaking up about 200 million years ago. Tectonics meaning building activity is the bases of the Theory of Continental Drift. 100 million years hence the world map can actually appear much much different from what it is today.

Planet Earth is enveloped by a thin blanket of gases, which we call the atmosphere. It is composed of three elements-gases, water vapour and dust particles. The atmosphere is composed mainly of nitrogen and oxygen, which make up about 99 per cent of clean, dry air. Nitrogen 78 %, Oxygen 21 % and other gasses like carbon dioxide, argon and others comprise 1 % by volume. Nitrogen helps in the growth of living organisms while oxygen is the breath of life.

The atmosphere appears to be very thin but there are actually seven or more layers in the atmosphere-each with its own characteristic.

Layers of Atmosphere : Three important layers are :

1. Troposphere : I extends upto 20 km above the ground and contains air.
2. Stratosphere: It extends from 20 to 50 km above the ground and contains the Ozone layer.
3. Ionosphere : It extends from 80 to 450 km above the ground. It contains electrically charged gas particles (ions) that reflect radio waves. Hence this layer is important for communications.

Humidity and Atmosphere: The amount of water vapour present in the air determines the humidity of the air. It varies from time to time and from place to place.

Humidity decreases with height in the troposphere because water enters the atmosphere through evaporation from the Earth’s surface. Higher the temperature, faster is the rate of evaporation.

Density of the Atmosphere : Air is a homogeneous mixture of gases. Due to the gravity of the Earth, this air, which is easily compressible, is squashed nearer the surface of the Earth. Therefore. the atmosphere is densest near the surface, i.e., nearly 80 % of the atmosphere is in the Troposphere, giving it the highest value of density. As altitude (height) increases, the density decreases.

Pressure and Atmosphere : Air may seem weightless but it is not. Gravity pulls the atmosphere down to the Earth. This is air pressure. Atmospheric pressure is defined as the weight of a column of air. The higher we go, there are less air. Hence the pressure decreases the altitude increases.

Temperature Distribution and Atmosphere: The Earth’s atmosphere is heated by the heat absorbed by the gas molecules and impurities like dust particles present in the air. Within the troposphere, temperature decreases evenly with increase in height.

Biosphere : Realm of Living Organism
Earth is the only planet of the solar system that supports life. Life is possible because of its unique hydrosphere, lithosphere and atmosphere.

The Lithosphere: The upper most layer of the Earth’s crust which is capable of supporting life is called soil. The soil provides nutrients for land organisms. It is also the medium for the fixation of plants. Minerals are cycled through the soil.

Hydrosphere: The water dissolves and supports nutrients. Water is used by plants for making food. It is also necessary for carrying out the chemical reactions within the body of living organisms.

Atmosphere : It maintains an even life supporting temperature on the earth. It (Ozone layer of atmosphere) protects living organisms from the harmful ultra-violet radiations of the Sun. The gases (O₂ and CO₂) present in air supporting life. Oxygen (O₂) helps in respiration, carbon dioxide (CO₂) in food manufacture by green plants and nitrogen in growth.

There are several species of organism that vary in size from microbes and bacteria to huge mammals.All the living organisms including humans are linked to each other and to the biosphere for survival. Biosphere supports about 10,00,000 varieties of animals and 3,00,000 varieties of plants. It includes minutes bacteria as well as huge trees and whales. The non-living component includes lithosphere, hydrosphere and atmosphere. It is known as physical environment.

The non-living organisms are broadly divided into two groups i.e. Plant Kingdom and Animal Kingdom. Plants produce their own food by the process of Photosynthesis, which is possible because of the solar energy. Animals cannot produce their own food themselves. They are dependent upon the plants directly or indirectly. All the food for the animals come from the vegetal world directly or indirectly. Man, being a part of the biosphere is also dependent upon the biosphere for his major needs.

What is Biosphere?
The narrow zone of contact between the land (lithosphere), water (hydrosphere) and air (atmosphere) is the biosphere. It is in this zone that life, that is unique to this planet, exists. Bios is an ancient Greek word meaning ‘life’. Life is biosphere is possible only because of a proper balance between land, water and air. Life exists on and in the ground (land), in water and in the air, the biosphere can be defined as the relatively narrow belt of living organisms found a little above the surface and a little below the surface of the Earth.

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 4 Rotation of the Earth offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 4 Question Answer – Rotation of the Earth

Objective Type Questions [1 mark each]

Question 1.
How much time does the Earth take for one rotation?
Answer:
23 hours 56 minutes 4 seconds.

Question 2.
State the direction of rotation.
Answer:
West to East.

Question 3.
Name the two ends of the axis of the earth.
Answer:
North pole and South pole.

Question 4.
At what angle is the axis of the earth inclined to the plane of the orbit?
Answer:
66 1/2°.

Question 5.
What is the speed of rotation at the equator ?
Answer:
1650 km / hour.

Question 6.
Which country is known as the land of the ‘midnight Sun’?
Answer:
Norway.

Question 7.
Which country is known as the land of the ‘rising sun’?
Answer:
Japan.

Question 8.
What is the average distance between the earth and the sun?
Answer:
150 million km.

Question 9.
What is the apparent movement of the sun and planets?
Answer:
iFrom east to west.

Question 10.
What causes flattering at the poles of the earth?
Answer:
Rotation.

Question 11.
What is meant by earth’s axis?
Answer:
Axis of the earth is an imaginary line on which the earth rotates.

Question 12.
We always see the sun rising in the east. Why ?
Answer:
Because the earth rotates from west to east.

Question 13.
Noon is hotter than morning. Why ?
Answer:
Because at noon sunrays are vertical.

Question 14.
Which movement of the earth causes day and night?
Answer:
Rotation.

Question 15.
How do you define day?
Answer:
The period taken for one rotation is called a day.

Question 16.
Which of the two places Cairo (30° E) or Chennai (80° E) will experience sunrise earlier?
Answer:
Chennai.

Question 17.
When it is noon along the Prime Meridian, which longitude will have mid-night ?
Answer:
180° longitude.

Question 18.
On which day the north pole has (i) 24 hours of daylight (ii) 24 hours of darkness ?
Answer:
21 June.

Question 19.
On which days all places on the earth have 12 hours of daylight and 12 hours of darkness ?
Answer:
21 March and 23 September.

Question 20.
What is known as the period of diffused light before sunrise ?
Answer:
Dawn.

Write short notes : [2/3 marks each]

Question 1.
Rotation of the earth.
Answer:
Rotation : The spinning of the earth on its axis from west to east is called rotation. The earth takes about 24 hours (23 hours 56 minutes 4 seconds) to complete one rotation. It is also known as daily motion of the earth.
Effects :

• Rotation causes days and nights.
• All heavenly bodies like sun, moon, planets appear to move from east to west.
• Tides occur regularly twice a day.
• Winds and ocean currents change their directions.
• The four main directions (north, south, east, west) can be determined with the help of rotation.
• We get a measure of time. A day consists of 24 hours-one complete rotation.
• The different times of a day like sunrise, noon, sunset, midnight can be determined due to rotation.

Question 2.
What are the effects of the inclination of the axis ?
Answer:

• There is apparent movement of the sun from the equator towards tropics.
• It causes opposite seasons in the two hemispheres.
• It results in the variation of length of day and night.
• When north pole is tilted towards the sun, the south pole turns away from the sun. So the two hemispheres are alternatively exposed to the sunrays.

Question 3.
What do you mean by Ferrel’s law ?
Answer:
At equator, the earth’s speed of rotation is about 1600 km per hour. The speed goes on decreasing poleward. At 60° latitude, it is 800 km per hour. This difference affects the general circulation of the atmosphere. Winds are deflectd to the right in the northern hemisphere and to the left in the southern hemisphere. Similarly, the ocean currents are also deflected. This is known as Ferrel’s law. Due to this the earth is flattened at the poles and bulged at the equator.

Question 4.
What is the effect of longitude on time?
Answer:
All the places located on the same meridian have the same local time. As the earth rotates from west to east, the places in the east will have sunrise earlier than places in the west. The places in the east gain time while the places in the west lose time. The Rule is (East – Gain – Add, West – Lose – Subtract).

Question 5.
What is a chronometer ?
Answer:
A chronometer is a highly accurate timepiece which is used to keep Greenwich Mean Time. The Greek word ‘chronos’ means time. It helps in determining the longitude of a place.

Question 6.
What do you mean by local time?
Answer:
Local time : The local time of a place is the time of its own meridian. The local time is calculated by the position of the sun at noon at a given place. When the sun at any place is highest in the sky, it is noon and it is 12 o’clock. All the watches of that place should be set according to that time.

Characteristics :

• Every meridian has a different local time.
• The places on the same meridian have the same local time.
• The eastern places will be ahead of western places for local time.
• Sundial was a simple and old method to determine local time.

Question 7.
What do you mean by standard time?
Answer:
Standard time : The standard time is the time of a central meridian of a country and is adopted by all the places. Standard time is a uniform time throughout a country. All the watches of the country are set according to this time. The Indian Standard Time (I.S.T.) is the local time of a place 82 1/2° E longitude which passes in between Allahabad and Mirzapur. It is 5 1/2° hours ahead of Greenwich Mean Time. When it is noon at Greenwich, it is 5.30 p.m. in India.

Short Answer-Type Questions : [3 marks each]

Question 1.
What are the results of the difference in the earth’s speed of rotation at various latitudes ?
Answer:
At equator, the earth’s speed of rotation is about 1600 km per hour. The speed goes on decreasing poleward. At 60° latitude, it is 800 km per hour. This difference affects the general circulation of the atmosphere. Winds are deflected to the right in the northern hemisphere and to the left in the southern hemisphere. Similarly, the ocean currents are also deflected. This is known as Ferrel’s Law. Due to this, the earth is flattened at the poles and bulged at the equator.

Question 2.
Why all the places south of the Antarctic Circle have 24 hours of darkness on June 21st ?
Answer:
On June 21st, it is winter solstice in southern hemisphere. The sun shines vertically on Tropic of Cancer. The South Pole-Antarctic Circle area is inclined away from the sun. So these places beyond Antarctic Circle have 24 hours of darkness.

Question 3.
What are the effects of the inclination of the axis?
Answer:

1. There is apparent movement of the sun from the equator towards tropics.
2. It causes opposite seasons in the two hemispheres.
3. It results in the variation of lengths of day and night.
4. When North Pole is tilted towards the sun, the South Pole turns away from the sun. So the two hemispheres are alternately exposed to the sunrays.

Question 4.
Why is dawn or twilight much shorter in duration at the equator than at polar areas?
Answer:
The brief period of refracted light between sunrise and full daylight is called dawn while that between sunset and complete darkness is called twilight. The sun rises and sets vertically at the equator. But the sun rises and sets obliquely in polar areas. So the period of dawn and twilight is longer in polar areas. As a result the sun takes longer time to pass through the refracted light.

Question 5.
On what dates is the sun overhead at the equator? What are these dates called?
Answer:
The sun is overhead at the equator on 23rd September and 21st March. These dates are called equinoxes meaning equal nights. 23rd September is known as autumnal equinox while 21st March is known as spring equinox.

Question 6.
Why is Norway called ‘the land of midnight sun’?
Answer:
Norway is located beyond Arctic Circle (66 1/2° N. latitude). In summer, on 21st June, the Sun never sets beyond the Arctic Circle. The polar areas have complete 24-hour continuous daylight. When there is midnight in other areas, the sun remains shining in Norway. So it is called the ‘land of midnight sun’.

Question 7.
Why is Japan called ‘the land of the rising Sun’?
Answer:
Japan is the easternmost country in the world. It is the first to receive sunrays as the earth moves from west to east. It has the sunrise earliest than other countries. So, it is known as the land of the rising sun.

Answer the following Questions : [5 marks each]

Question 1.
How are days and nights occurred ?
Answer:
Days and nights are occurred due to rotation of earth. The earth rotates on its axis from west to east. When it rotates, one half of the earth turns towards light and has, therefore, day. The other half turns away from the sun and remains in darkness and has night. During 24 hours, every part of the earth comes in turn before the sun and then goes into the darkness. Therefore, the position of day and night keeps on changing. When it is day in one hemisphere, it is night in the other.

Question 2.
Account for the unequal length of day and night.
Answer:
The length of day and night varies throughout the year. Sometimes the days are longer and nights are shorter or vice versa. It is due to two reasons :

• The inclination of the axis.
• The revolution of the earth.

Due to the inclined axis, one hemisphere leans towards the sun for the six months, the other hemisphere leans towards the sun for the next six months. In summer, on 21st June, days are longer in northern hemisphere and the nights are shorter. In winter, the conditions are reversed, the days are shorter and nights are longer in the northern hemisphere. If the axes were vertical there would have been equal days and nights everywhere.

Question 3.
(a) What is International Date Line?
(b) What is its necessity ?
(c) Explain its location.
Answer:
(a) The International Date Line is an imaginary line roughly corresponding to 180° meridian. Ships crossing this line change the date by one day.

(b) Necessity : A traveller going eastwards will be 12 hours ahead of G.M.T. (Greenwich Mean Time) till he reaches 180° east meridian. Similarly, he loses 12 hours when he reaches 180° west going westwards. Thus, there is total difference of 24 hours or a whole day at the 180° meridian. This causes a confusion of dates when travelling around the world. To avoid this confusion, nations have agreed upon the Internation Date Line to change dates. When Magellan returned in Spain in 1522 after travelling around the world, he thought he had arrived on the 5th of September. He was shocked to be told that the date was 6th september. As he travelled westward, he knew nothing about the day he had lost.

(c) Location of Date Line : The International Date Line passes through the Pacific Ocean forms North to South following 180° meridian. It avoids the land areas and deviates from 180°. This is done so that it does not divide group of islands under the same government. The date line goes zigzag to avoid the confusion of time between one island and another. It bends to the west of 180° to avoid the Aleutian islands. In the southern hemisphere it bends eastward to avoid Fiji and Tonga islands.

Question 4.
What is the rule of changing the date while crossing the International Date Line ?
(a) What is meant by ‘six-day week’ and ‘eight-day week’?
(b) Explain the above with the help of a map.
Answer:
Rule: On crossing the date line, the ships adjust the dates according to the following rules :
(a) When crossing westward towards Asia (from USA to Japan), a day will be added. When crossing the date line, ship misses a day from the calendar and have ‘six-day week’. If a ship crosses the date line on Monday, the next day will be Wednesday and not Tuesday.

(b) When crossing eastward towards America (from Japan to U.S.A) a day must be subtracted. When crossing the date line ships gain a day from the calendar and have an ‘eight-day week’. It repeats a day. If ship crosses the date line on Monday, the next day will be again Monday and not Tuesday.

Question 5.
Why do we have standard time?
Answer:
The local time of places which are on different meridians are bound to differ. For instance, it will be difficult to prepare a time table for trains which cross several longitudes. In India, for example, there will be a difference of about 1 hour and 45 minutes in the local times of Dwarka in Gujarat and Dibrugarh in Assam. It is, therefore, necessary to adopt the local time of some central meridian of a country as the standard time for the country. The longitude of 82 1/2° E (82° 30° E) is treated as the Standard Meridian in India. The local time at this meridian is taken as the standard time for the entire country. It is called the Indian Standard Time (IST).

Kabeer lives in Bhopal. He tells his friend Alok that they will not be able to sleep tonight. A day and night cricket match between India and England had started at 2 p.m. in London. This means that the match would begin at 7:30 p.m. in India and finish well in the night. Do you know what is the time difference between India and England ?

India located east of Greenwich at 82° 30′ E is 5 hours and 30 minutes ahead of GMT. So, when it is 2:00 p.m. noon in London, it will be 7:30 p.m. in India.

Some countries have adopted more than one standard time because they have a great longitudinal extent. For example, in Russia, there are as many as eleven standard times. The earth has been divided into twenty-four time zones of one hour each. Each zone thus covers 15° of longitude.

Identify the correct answers : 1 mark each

Question 1.
Deflection of wind on the Earth’s surface is caused by
(a) Revolution of the earth
(b) Rotation of the earth
(c) Attraction of the moon
Answer:
(b) Rotation of the earth

Question 2.
Rotation is the movement of the earth round the
(a) Sun
(b) on its axis
(c) round the universe
(d) round the earth
Answer:
(b) on its axis

Question 3.
The speed of rotation of the earth at the equator is
(a) 1550 km per hour
(b) 1650 km per hour
(c) 1639 km per hour
(d) 1570 km pr hour
Answer:
(b) 1650 km per hour

Question 4.
The sun rises in the east and sets in the west due to
(a) rotation of the earth
(b) rotation of the moon
(c) revolution of the earth
(d) revolution of the moon
Answer:
(a) rotation of the earth

Question 5.
The earth rotates on its axis once in
(a) 23 hours
(b) 24 hours 30 minutes
(c) 23 hours 56 minutes 4 seconds
(d) 22 hours
Answer:
(c) 23 hours 56 minutes 4 seconds

Question 6.
The time when the sun is at the highest position in the sky is called
(a) morning
(b) noon
(c) evening
(d) twilight
Answer:
(b) noon

Question 7.
The International Date Line follows the
(a) 0°
(b) 145°
(c) 180°
(d) 80 meridians of longitude
Answer:
(c) 180°

Question 8.
The spinning of the earth on its axis is called
(a) revolution
(b) travelling
(c) speed
(d) rotation
Answer:
(d) rotation

Question 9.
The speed of rotation of the earth at the poles is
(a) 0 km / hour
(b) 990 km / hour
(c) 1530 km / hour
(d) 1650 km / hour
Answer:
(a) 0 km / hour

Question 10.
The circular boundary between the sun-lit part of the sphere and the part in darkness is known as the
(a) latitude
(b) longitude
(c) shadow circle
(d) equator
Answer:
(c) shadow circle

Fill in the blanks with correct words [1 mark each]

Question 1.
The axis of the earth is inclined at an angle of ____ from the orbital plane.
Answer:
66 \(\frac{1}{2}\) °

Question 2.
The speed of rotation is negligible at the ____.
Answer:
poles

Question 3.
Everyday the earth makes a journey across the sky from _____ to _____.
Answer:
west, west

Question 4.
The movement of the earth on its axis is called _____.
Answer:
rotation

Question 5.
The earth’s axis always points to the ______.
Answer:
pole star

Question 6.
Our shadow is the at _____ the noon time or mid-day.
Answer:
minimum

Question 7.
The local time at P(40° N, 40° E) is 12 noon on Sunday. The local time at B (40° N .130° E) will be _____ on Sunday.
Answer:
6 p.m.

Question 8.
A (20° N . 60° E), B(60° S . 60° E) and C (20° N, 20° E) are places on the earth. ____ of these will have the same local time.
Answer:
A and B.

If the sentence is true, write ‘T’ and if false write ‘F’ against the following : 1 mark each

1. The Earth’s axis is an imaginary line joining poles and passing through the equator.
Answer:
False

2. The circular boundary between the sun-lit and dark part of the earth is known as shadow circle.
Answer:
True

3. Actually the sun does not move from east to west.
Answer:
True

4. Rotation is also known as the annual movement of the earth.
Answer:
True

5. The city of Kolkata at 88° 34′ E is considered as the Standard Meridian of India.
Answer:
False

6. The hours beginning from mid-night to noon is indicated by a.m.
Answer:
True

7. The axis of the earth makes an angle of 23 1/2° with the vertical.
Answer:
False

Write the differences: [2/3 marks each]

Question 1.
A.M. and P.M.
Answer:

A.M.	P.M.
1. The word ‘meridian’ means mid-day or noon. A.M. = Ante-meridian or before noon. (Ante = before)	1. P.M. = Post-meridian or afternoon (Post = After)
2. The period of time from 12 midnight to just before 12 noon is called ante-meridian (a.m.)	2. The period from 12 noon to just before midnight (12.00) is called postmeridian (p.m.)

Question 2.
Dawn and Dusk.
Answer:

Dawn	Dusk/Twilight
1. Just before sunrise, there is some diffused light. This period is called dawn.	1. Just before sunset, diffused light is left. This period is called dusk.
2. Dawn lasts till the sun rises and begins when the centre of he sun arrives below the apparent horizon 6° (for civil down) / 12° (for nautical dawn) / 18° (for astronomical dawn).	2. Dusk continues till the centre of the sun sinks below the horizon 6° (for civil twilight) / 12° (for nautical twilight) / 18° (for astrono-mical twilight).
3. Dawn at the equator is the shortest as the sun rises there in vertical path.	3. Dusk at the equator is the shortest as the sun sinks there in vertical path.

Question 3.
Local time and Standard time.
Answer:

Local time	Standard Time
1. Local time of a place is the time of its meridian.	1. Standard time is the time of a central meridian of an area.
2. Each place has its own local time.	2. All places have uniform or same time.
3. When it is noon, the local time is 12 o’clock.	3. It does not have any relation with noon or height of the sun.
4. All places on a meridian have same local time.	4. All places within a country have the same standard time.
5. The places in the east are ahead of west in time. For 1° longitude there is a difference of 4 minutes of time.	5. There is no change in time. So it is known as standard time.

Rotation of the Earth Class 6 WBBSE Notes

Axis of the Earth : The Earth rotates about its axis. It is inclined at an angle of 66 1/2° to the plane of the orbit.

Movements of the Earth : The Earth has two movements : (i) The Rotation and (ii) Revolution.

Rotation : Rotation is the spinning of Earth on its axis. Greek astronomer, Aristarchus of Samos (325-250 BC) stated that. It is the earth, and not the stars, that spins everyday.

Direction : Rotation is the turning around of the Earth on its axis, from west to east.

Effects : Day and night are caused due to daily motion of the earth. The earth depends upon the sun for its light. The sun can face only one half of the earth.

Everyday we see that the Sun rises in the east and sets in the west. It seems as if the Sun travels round the earth from east to west. This is known as ‘apparent movement of the Sun’. But the fact is otherwise. Actually the Sun does not rise or set. Like all other planets in the Solar System, the Earth also has two types of movements. The Earth rotates on an imaginary axis. It takes nearly 24 hours for the Earth to complete one rotation. The period taken for one rotation is called a day.

Movements of the Earth : In 1522 A.D., Nicolaus Copernicus, a Polish astronomer proved first in his book titled ‘On the Revolutions of the Heavenly Spheres’ that the earth spins daily on its axis and goes around the Sun every year along with the other planets of the Solar System. The Earth has two main motions or movements-
1. Rotation and 2. Revolution.

Rotation of the Earth:

Definition : The Earth spins on its own imaginary axis (66 1/2° inclined to its orbital plane) from west to east once in every 24 hours (23 hours 56 minutes and 4 seconds). This spinning of the Earth is termed as rotation. The rotation is called ‘diurnal motion’ of the Earth as it causes formation of day and night. This diurnal movement is also known as ‘the daily movement of the Earth’. According to A.N. Strahler, “The spinning of the Earth on its polar axis is termed as rotation”.

Salient features of the Earth’s Rotation:

Direction of Rotation : If we look the Earth (Globe) from outside, the Earth is found to rotate from west to east or in anti-clockwise direction. Since the Earth rotates in a west-east direction, we see the Sun rising everyday in the east and setting in the west.

Axis :

1. Rotation is the turning around of the Earth on its axis, from west to east.
2. The axis is the imaginary line passing through the centre of the Earth on which the Earth rotates.
3. The Earth spins, west to east, around its axis once in 24 hours.
4. The north pole and south pole lie at the ends of the axis.
5. The Earth’s axis is not vertical. It makes an angle of 23 1/2° with the vertical or 66 1/2° with the plane of the Earth’s orbit.
6. The Earth’s axis always remains pointed in the same direction (towards the Pole star) as the Earth goes around the Sun.
7. The tilt of the Earth axis is also known as the inclination of the Earth’s axis.

The Speed of Rotation : Being spherical in shape, the surface speed of rotation of the Earth is variable. It is highest at the equator, gradually diminishing towards north and south and becomes zero at the poles. The surface speed at the equator (0°) is 1630 km / hr.

Why do we not feel the Rotation of the Earth? We do not feel that the Earth on which we live because it is constantly rotating. The reasons are-

(i) There are no heavenly objects nearer to the Earth, either stationary or moving opposite of the Earth’s rotation by which we can compare the Earth’s rotation.

(ii) The rate of rotation is uniform and constant for each place on the Earth’s surface.
(iii) The atmosphere also rotates with the Earth uniformly.

What are the effects of the speed of rotation: The differences in the speed of rotation at the Equator and at the poles has important consequences.

1. It affects the shape of the Earth : The rotation of the Earth is considered responsible for the slight flattening of the Earth at the two poles and bulging at the equator. The equatorial diameter is 43 km longer than the polar diameter.

2. It affects the general circulation of the atmosphere and ocean currents :
(a) The moving air and ocean water in deflected at the right in the northern hemisphere and to the left in the southern hemisphere.
(b) Cyclones and anticylones are similarly deflected in both hemispheres.
(c) The movements of water in the ocean is affected in relation to rigid crust.

Effects of Earth’s Rotation –

The rotation of the Earth is responsible for the following major effects :

• Formation of days and nights
• Occurrence of sunrise, noon and sunset
• Determination of time
• Deflection of planetary wind
• Formation of tides
• Magnetization of the Earth
• Differentiation of temperature
• Determination of the direction
• Different local time
• Shape of the Earth
• Other.

Formation of Days and Nights : The Earth rotates around its axis from west to east once in 24 hours. So when a particular place comes in front of the Sun, it gets the sunlight and therefore experiences day. As the earth rotates, this particular place moves away from the Sun into darkness. The imaginary line that separates the lit-up half from the darkened half is called the circle of Illumination or Shadow Circle. In this way all places on the Earth’s surface continuously experience periods of daylight followed by periods of darkness called night.

Occurrence of Sunrise, Noon and Sunset : As the Earth rotates, the portion of the Earth which starts turning towards the Sun has sunrise. Slowly the inclination of the sunrays increases. When it is maximum, it is noon. When that portion gets away from the Sun, evening appears and soon the sun sets. The positions of the Earth’s various parts continue to pass through these conditions as the Earth continues to rotate.

Determination of time : The Earth takes a full day to make a complete rotation. We divide the day in 24 hours and then an hour into 60 minutes and a minute into 60 seconds. Thus we get an idea of calculating time.

Deflection of planetary wind : In 1835, Gustave-Gaspard de Coriolis explained that air flows do not move in a straight path because the spinning of the Earth on its axis causes the air masses to get deflected. The tendency of deflection of wind due to the Earth’s rotation is known as the Coriolis effects or the Coriolis force. After investigating and analysing the Coriolis force, this concept was developed by the American climatologist William Ferrel in 1855.

According to Ferrel, due to the effect of Coriolis force, wind and ocean currents are deflected towards the right in the northern hemisphere and towards the left in the southern hemisphere. This is known as Ferrel’s Law.

Alternation or Formation of Day and Night –

As the Earth is a sphere, only half of it, facing the Sun, is lit-up by sunrays. The other half remains dark. As a result, day occurs in the lit-half of the earth and night in the dark-half of it. The imaginary line that separates the lit-up half from the darkened half is called circle of Illumination or shadow circle. Each place of the surface of the Earth is swept over twice by the shadow circle once at dawn and again at twilight everyday.

The Earth’s rotation does not allow either of the two halves to remain always lit or unlit. They keep moving from sunlight to darkness and again from darkness to sunlight after almost regular intervals. The process of this change is not sudden. Transformation from sunlit day to night darkness and again from night darkness to sun-lit day at each place is uniform and ceaselessly gradual at almost regular intervals. During each 24 hour day, each place or meridian appears to shift its position from west to east. Hence from any place or meridian the Sun appears to move from east to west. This phenomenon may be cited as a proof that the earth rotates from west to east in respect of the Sun.

A Causes of dawn, sunrise, noon, evening, twilight (or dusk) and mid-night: All these phenomena occur in a complete 24 hour day. No place on the Earth has an abrupt change from day to night or vice versa. There is a transition period between day and night as well as night and day. During this transition period, there is diffused light produced by scattering and reflection by clouds, dust and other particles present in the atmosphere. These occur both before sunrise and after sunset.

Dawn : The period of receiving refracted and reflected sunlight before sunrise is called dawn. However the period of diffused light before sunrise is called dawn. Dawn lasts until the sun rises and begins when the centre of the sun arrives below the apparent horizon 6° (for civil dawn) / 12° (for nautical dawn) / 18° (for astronomical dawn). Dawn at the equator is the shortest as the sun rises there in vertical path, at the temperate latitudes longer and at the poles it much longer.

Sunrise: The time at which the upper edge of the sun appears above the apparent horizon of a place on the Earth’s surface on a clear day is called sunrise. The Earth rotates around its axis from west to east makes the Sun appear to rise in the east and it is known as sunrise.

Noon : The time at which the Sun stands at its highest position or at in vertical position above the horizon of a place on the Earth surface is called noon.

Evening : Similarly the time at which the upper edge of the Sun appears to sink below the apparent horizon of a place on the Earth’s surface is called evening. Thus when the Sun sets at a particular place it is called evening. D

Twilight or Dusk : The period on diffused light before sunset is called twilight. Twiligh’t or dusk at a place or the Earth’s surface begins after sunset and continues till the centre of the Sun sinks below the horizon 6° (for civil twilight) / 12° (for nautical twilight) / 18° (for astronomical twilight).

Account for the unequal length of day and night : The tilting of the Earth axis is called the inclination of the Earth’s axis. The length of day and night varies throughout the year. It is due to the inclination of the Earth’s axis. Due to inclined axis, one hemisphere leans towards the Sun for the six months, the other hemisphere leans towards the Sun for the next six months.

Effect of the Inclined Axis –

Assume the Earth’s axis to be vertical –

1. Place A on the Equator would be on position A’ after 12 hours
2. Place B on the Tropic
of Cancer would be at position B’ after 12 hours.
Distance BX = Distance XB’
∴ Length of day = Length of night.
3. Similarly at the poles, or at any other place on the Earth, lengths of day and night would be equal if the axis of the Earth was not inclined.

Now consider the effect of the inclined axis –

1. Place A at the Equator would be at position
A’ after 12 hours
Distance AO = Distance OA’
∴ Length of day = Length of night

2. Place B on the Tropic of Cancer will be at position B’ after 12 hours.
But distance BX is not equal to distance XB’. BX is greater than BX’. This means that the length of day is greater than the length of night.
∴ Days are longer than nights

3. Place C on the Arctic Circle will be at position C’ after 12 hours. Even after 12 hours, place C remains in light (C’). In summer, the Sun does not set for six months in the region beyond the Arctic Circle.
∴ Day of 24 hours near the poles

4. Place P on the Tropic of Capricorn in the southern hemisphere will be at position P’ after 12 hours. Distance PQ (in light) is less than the distance QR (in darkness)
∴ Days are shorter than nights
Place S remains in continuous darkness.

Shadow Circle or Circle of Illumination : The Earth is spherical in shape. Its circumference is about 40,000 km while its diameter is about 12756 km in the west-east direction, the direction in which the Earth rotates. The Earth completes one round of rotation in about twenty-four hours. As the Earth rotates, the sun-lit side gradually moves away from the Sun into darkness (at sunset) and the side that was away from the Sun and had darkness gradually moves into daylight (at sunrise).

The circular boundary between the illuminated or sun-lit part of the sphere and the part in darkness is known as shadow circle or the circle of illumination.

Earth’s Rotation and Concept of Local Time : Owing to the spherical shape of the Earth only one half of the Earth is illuminated by the Sun at any given time. The other half is dark and experiences night. As the Earth rotates from west to east, the zone of illumination also moves slowly towards the east. Local time is one which is fixed in relation to the position on the Sun at that place or that meridian. When the Sun is overhead in the sky, it is mid-day or 12 noon.

We keep time in synch with the apparent daily movement of the Sun. The Earth completes one rotation approximately in 24 hours. 1 minute is obtained as we split each hour into 60 equal parts and 1 second is obtained by splitting a minute into 60 equal parts.

Change of Time and Date :

Ferdinand Magellan and his team who started their circumnavigation expedition in 1519 and when they returned at the end of the voyage, they found out something weird. The calendars back home were not at all matching with their calculations of time and date. They showed Tuesday when the mariners thought it was Monday.

Owing to the spherical shape of the Earth, only one half of the Earth is illuminated by the Sun at any given time. The other half is dark and experiences night. As the Earth rotates from west to east, the zone of illumination also moves slowly towards the east. This accounts for the variation of time and also the date. The Sun rises in the east as the earth rotates from west to east once in every 24 hours. So, places on the Earth located more towards the east are ahead in time than those to the west.

Sense of Date: By a common consensus the longitude of Greenwich, a place near London in England (U.K.), has been accepted as 0°. The Earth rotates on its axis once in 24 hours. It means that it takes 24 hours to pass through 360 degrees or 360° of longitude. In other words, it takes 24 hours to pass through 1° longitude. Thus, if we know the meridians of longitude of two places, we can find out the difference in their local times.

The local time at a place is fixed with reference to the apparent movement of the Sun. When the Sun is overhead in the sky, it is mid-day or 12 noon. In the morning, the length of the shadow is long. As the Sun moves up in the sky, the length of the shadow goes on decreasing. The length of the shadow is shortest when the position of the Sun is overhead at noon. In the afternoon, as the Sun moves down, the length of the shadow increases gradually. All places along a line of longitude have the same local time. The local time at places on different longitudes.

International Date Line : 180° is the same longitude which is numbered as 180° E and 180° W. This longitude is just opposite to that of the Greenwich Meridian [0°]. A peculiar situation arises at 180° long.

This may be illustrated with an example. When the time is 6 p.m. on Monday, 25th December at Greenwich, the time at 180° E long will be 12 hours ahead of G.M.T. The time at 180° E will be 6 a.m. on Tuesday, 26th December. The time at 180° W longitude will be 12 hours. behind that of the G.M.T. or 6 a.m. on Monday, 25th December. Thus when the time is computed eastwards, the time is 6 a.m. on Tuesday, 26th December. When the time is computed westwards, it is 6 a.m. on Monday, 25th December. Thus on either side of the 180° longitude there is a time difference of 24 hours or one day. In which longitude should the correction of date be made ? By international agreement, the correction of date is made along the 180° longitude line. This called the International Date Line.

While travelling eastwards, a date is repeated. For example, the time is 6.am. on Tuesday, 26th December, at 180° E, but on crossing the longitude, the time is 6 a.m. on Monday, 25th December. As a result of crossing at the international Date Line eastwards, the Christmas day gets repeated. The person celebrates two Christmas days on successive days. Again if a person crosses the International Date Line westwards, one day is lost. For example, it is 6 a.m. on 25 th December at 180° W. After crossing International Date Line, the time is 6 a.m. on 26th December. The Christmas day is lost owing to the crossing on the Date Line.

Why is the International Date Line not straight ?

The International Date Line passes through the Pacific Ocean. It deviates from 180° longitude in some places in order to keep all the islands under one administration on one side of the Date Line. The Date Line goes zigzag in some places to avoid land and to leave island groups wholly on the same side of the line. The Dare Line deviates eastwards in the Bering Straits between Alaska and Siberia. The line deviates westwards (7°) of 180° longitude to include the entire Aleutian islands to the east of the line. Further south, the Date line deviates eastwards (11°) of 180° around Fiji and Tonga islands. These islands keep the same date as New Zealand.

Duration of twilight :

The duration of twilight at a place depends on the path of the Sun in the sky.
(i) In the low latitudes, where the sun’s path is almost vertical, the duration of twilight is short. The sun sinks below the horizon rapidly.
(ii) In the middle and high latitudes, where the sun has an inclined path at a low angle, the duration of twilight is

Interna-tional Date Line :

The International Date Line may be defined as an imaginary line drawn almost along 180° meridian extending from the north pole to the south pole from which each new date starts and each date ends at last.

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 3 Location of a Place on the Earth’s Surface offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 3 Question Answer – Location of a Place on the Earth’s Surface

Objective Type Questions :

Question 1.
What is the latitude of equator?
Answer:
0°

Question 2.
What is the latitude of Tropic of Cancer?
Answer:
23 \(\frac{1}{2}\)° North

Question 3.
What is the latitude of Arctic Circle ?
Answer:
66 \(\frac{1}{2}\)° North

Question 4.
What is the latitude of Tropic of Capricorn?
Answer:
23 \(\frac{1}{2}\)° South

Question 5.
What is the latitude of Antarctic Circle?
Answer:
66 \(\frac{1}{2}\)° South

Question 6.
Which is the longest line of latitude?
Answer:
Equator

Question 7.
Which latitudes are known as low latitudes?
Answer:
0° to 30°

Question 8.
Which latitudes are known as Mid latitudes?
Answer:
30° to 60°

Question 9.
Which latitudes are known as High latitudes?
Answer:
60° to 90°

Question 10.
Which star is located vertically above the North Pole?
Answer:
Pole-Star

Question 11.
How many lines of latitude are there?
Answer:
180 + 1 = 181

Question 12.
How many lines of longitude are there?
Answer:
360 – 1 = 359

Question 13.
What is the location of international date line?
Answer:
180° E – W meridian

Question 14.
Which meridian is called Prime Meridian?
Answer:
0° meridian

Question 15.
What is the value of equator?
Answer:
0° latitude

Question 16.
What is the value of Prime Meridian?
Answer:
0° longitude

Question 17.
What is the approximate distance covered by 1° latitude?
Answer:
111 km

Question 18.
What is the difference of time for 1° of longitude?
Answer:
4 minutes

Question 19.
Name the two basic lines of reference for location of a place on Earth.
Answer:
Prime Meridian and equator

Question 20.
What does the word ‘meridian’ mean?
Answer:
‘Mid-Day’

Question 21.
Into how many time zones, has the world been divided ?
Answer:
24

Question 22.
Where is the place, Greenwich located?
Answer:
On 0° longitude (Britain) near London

Question 23.
Who devised the lines of latitude and longitude?
Answer:
Eratosthenes

Question 24.
Name the two hemispheres of the Earth made by the equator.
Answer:
Northern and Southern Hemisphere

Question 25.
Name the thermal zones of the Earth.
Answer:
Tropical, Temperate and polar.

Question 26.
Which temperature zone receives almost vertical rays of the Sun?
Answer:
Tropical Zone.

Question 27.
Which temperature zone receives slanting rays?
Answer:
Polar Zone.

Question 28.
Which line of longitude is used to fix the world standard time?
Answer:
Prime Meridian – 0°

Question 29.
How can the position of a place be fixed on a map?
Answer:
With the help of latitude and longitude of a place.

Question 30.
What is meant by ‘parallels of latitude’?
Answer:
Lines of latitude

Question 31.
What do you mean by meridians?
Answer:
Lines of Longitude

Question 32.
What is a small circle?
Answer:
A circle which does not bisect the Earth into two equal halves.

Question 33.
What is the relation between Temperature and Latitude of a place?
Answer:
The temperature decreases with latitude.

Question 34.
What is latitude of North Pole and South pole?
Answer:
90° N and 90° S

Question 35.
What name is given to 23 \(\frac{1}{2}\)° North latitude?
Answer:
Tropic of Cancer

Question 36.
What name is given to 23 \(\frac{1}{2}\)° South latitude?
Answer:
Tropic of Capricorn

Question 37.
What is latitudinal value of Arctic circle and Antarctic circle ?
Answer:
66 \(\frac{1}{2}\)° N and 66 \(\frac{1}{2}\)° S

Question 38.
Where is the equator situated ?
Answer:
In the middle of the Earth (Between North Pole and South Pole).

Question 39.
What is a grid (Earth Grid) ?
Answer:
It is a network of parallel and meridians on a globle. It is also called geographic grid.

Question 40.
Why are the letters N or S added to latitude values?
Answer:
The latitudes in Northern hemisphere are marked N while the latitude in Southern hemisphere marked S.

Question 41.
What is the importance of Tropic of Cancer?
Answer:
It marks the Northern Limit of Tropical Zone.

Question 42.
What is the importance of Tropic of Capricorn?
Answer:
It marks the Southern Limit of tropical zone.

Question 43.
Name the two reference lines with respect to which the distances of various places on the Earth’s surface are measured?
Answer:
Prime Meridian and Equator.

Question 44.
How is the latitude of a place found zone?
Answer:
With the help of Pole Star.

Question 45.
What are the limits of the tropical zone?
Answer:
23\(\frac{1}{2}\)° N and 23\(\frac{1}{2}\)° S

Question 46.
What is the North Temperate Zone?
Answer:
The Zone between 23 \(\frac{1}{2}\)° N – 66 \(\frac{1}{2}\)° N

Question 47.
What is the South Temperate Zone?
Answer:
The Zone between 23 \(\frac{1}{2}\)° S – 666 \(\frac{1}{2}\)° S.

Question 48.
By how many lines is the equator intersected?
Answer:
359

Question 49.
Why are letters E or W added to longitude values?
Answer:
The longitudes in the Eastern hemisphere are marked E while the longitudes in the Western hemisphere are marked W.

Question 50.
What are holes on the Earth?
Answer:
The Pole pointing towards Pole Star is called North pole while the opposite pole is called South Pole.

Define the following briefly : 2 marks each

Question 1.
What do you mean by latitude?
Answer:
Latitude is the angular distance of a place North or South of plane of equator.

Question 2.
What do you mean by longitude?
Answer:
Longitude is the angular distance of a place East or West of the Prime Meridian.

Question 3.
What is Graticule ?
Answer:
The network of parallels and meridians is called graticule.

Question 4.
What is Equator?
Answer:
Equator is an imaginary circle bisecting the Earth into two equal halves.

Question 5.
Define ‘Latitude’ and ‘Longitude’ of a place.
Answer:
Latitude is the angular distance of a place North or South of the equator. Longitude is angular distance of a place East of West of Prime Meridian.

Question 6.
What are the uses of lines of latitude?
Answer:

1. We can find out the average temperature of a place with the help of latitude.
2. We can find out the distance of a place from the equator ( 1 % latitude = 111 km )
3. We can determine the location of a place.

Question 7.
What is the main function of longitude in Mathematical Geography?
Answer:
Longitude’s main function is to determine local time of a place in relation to
Greenwich mean time or world time. It is useful in determining the location of a place on the Earth.

Question 8.
(a) What do you mean by ‘Grid’ ?
(b) Which lines from the grid ?
(c) What is the use of this grid ?
Answer:
The lines of latitude and the lines of longitude intersect to form a geographic Grid System. This grid is located on a globe. It helps to find the exact location of places on Earth.

Question 9.
What is meant by ‘Graticule’ or ‘Earth Grid’ ?
Answer:
Lines of longitude and lines of latitude are drawn to determine the location of a place on the Earth. This complete network of parallels and meridians is called ‘graticule’ or ‘Earth Grid’. The term Grid is used for a network of crossing lines.

Question 10.
How will you find the latitude of a place with the help of Pole Star?
Answer:
Pole Star always points towards the North Pole. The altitude of the Pole Star is same as the latitude of a place in the northern hemisphere.

Question 11.
How will you determine the latitude of a place with the help of the Sun ?
Answer:
The latitude of a place can be determined by measuring the altitude of the Sun at mid-day. The mid-day altitude of the Sun is subtracted from 90°. It gives Zenith distance (i.e., the angle of the Sun with the Zenith of a place). The latitude of a place can be determined with the help of the following rule :
Latitude of a place = Zenith distance pm Declinaion of the Sun.

Answer the following questions : 5 marks each

Question 1.
Mention the properties of parallels of latitude.
Answer:
Important Properties of Parallels :

1. A latitude is the angular distance of a place north or south of equator.
2. The maximum value of latitude is 90°.
3. The total number of latitudes including equator are 89 + 1 + 89 = 179
4. Parallels are always parallel to one-another.
5. Being parallel to each other the parallels never intersect each other
6. Parallels except North Pole and South Pole are circular lines but not of the same size.
7. As the latitude increases, the circumference of the parallel decreases.
8. The parallels of latitude run in the east-west direction.
9. The distance between any two consecutive parallels remains almost same and it is about 111 k.
10. All parallels except North Pole and South Pole intersect meridians at right angles.
11. All parallels except the equator are small circles.
12. Every point on the earth lies on parallel of latitude.
13. The place lying on the same parallel receive almost the same heat but local time differs from place to place.

Question 2.
What are the importance or uses of parallels of latitudes?
Answer:
Importance of uses of Parallels of Latitude :

1. Parallels help us to guess what type of climate would prevail in a particular place.
2. To find out the exact position of a place on the earth’s surface we need both the lines of latitude and longitude.
3. The parallels of latitude enable us to know the distance of a place from the equator and they can be used to determine the scale of a map.

Question 3.
What are the properties of Meridians ?
Answer:
Important Properties of Meridians :

1. Longitude is the angular distance of a place east or west of the Prime Meridians
2. There are 360 meridians of longitude.
3. The meridians are not parallel. They converge at the two poles.
4. The meridians are semi-circles.
5. All meridians are of equal length
6. The distance between any two merdians are of equal. They get closer from the equator to the poles.
7. All meridians run in a true north-south direction.
8. All places on the same meridian have sunrise, noon or sunset at the same time.
9. Each meridian cuts the equator at right angle.

Question 4.
Distinguish between the Parallels of Latitude and meridians of Longitude.
Answer:
Difference between latitude and longitude

Points of differnece	Parallels of latitude	Meridians of longitude
1. Orientation	Parallels are extended in eastwest direction	Meridians are extended in north-south direction.
2. Extent	Parallels are extended in eastwest direction	Meridians are extended in north-south direction.
3. Types	They are parallel to each other.	They are not parallel.
4. Highest	The highest possible latitude is 90°.	The highest possible longitude is 180°
5. Total No.	There are 89 parallels in both the hemisphere at an interval of 1°. The total is 179.	There are 180 meridians in both the hemisphere. The total in 360.
6. Length	From the equator towards the poles the parallels are getting smaller in length.	Meridians remain uniform in length.
7. Climate	Parallels are related to climatic belts.	Meridians are related to local time.
8. Angle	Total angular measurement is 360°.	Total angular measurement is 180°.

Question 5.
Distinguish bewteen Great Circle and Small Circle.
Answer:

Great Circle	Small Circle
1. A great circle is a circle which bisects the Earth into two equal hemispheres.	1. A small circle is a circle which does not bisect the Earth into two equal hemispheres.
2. It passes through the centre of the Earth.	2. It does not pass through the centre of the Earth.
3. It has circumference of 2 πR.	3. It has a circumference less than 2π R.
4. All meridians and Equator are great circles.	4. All parallels except Equator are small circles.
5. Ships follow great circle as it is the shortest distance between two points.	5. Ships do not follow small circle routes.

Question 6.
Distinguish between latitude and longitude of a place.
Answer:

Latitude	Longitude
1. Latitude is the angular distance of a place North or South of the Equator.	1. Longitude is the angular distance of a place East or West of Prime Meridian.
2. The latitude value-increases in NorthSouth directions from the Equator.	2. The longtidue value increases in EastWest directions from Meridian.
3. Its value ranges between 0° to 90° N, 0° to 90° S.	3. Its value ranges between 0° to 180° E, 0° to 180° W

Question 7.
Distinguish between Equator and Prime Meridian.
Answer:

Equator	Prime Meridian
1. Equator is a circle around the Earth bisecting it into two equal parts.	1. The prime meridian is a semicircle joining north pole and south pole.
2. It is 0° latitude.	2. It is 0° longitude.
3. It passes through the centre of the Earth.	3. It passes through the Greenwich (London).
4. It divides the Earth into northern and southern hemispheres.	4. It divides the Earth into eastern and western hemispheres.

Question 8.
Distinguish between the Tropic of Cancer and Tropic of Capricorn.
Answer:

Tropic of Cancer	Tropic of Capricorn
1. 23 1/2° N Latitude is known as Tropic of Cancer.	1. 23 1/2° S Latitude is known as Tropic of Capricorn.
2. It lies in the northern hemisphere.	2. It lies in the Southern hemisphere.
3. The Sun shines vertical on it on 21 st June.	3. The Sun shines vertical on it on 22 nd December.
4. It is the northern limit of tropical region.	4. It is the southern limit of tropical region.

Question 9.
Distinguish between the Arctic circle and Antarctic circle.
Answer:

Arctic circle	Antarctic circle
1. 66 1/2° N parallel is known as Arctic circle.	1. 66 1/2° S parallel is known as Antarctic circle.
2. Beyond this lies the northern polar region.	2. Beyond this lies the southern polar region.
3. Beyond Arctic circle the length of day is more than 24 hours in summer.	3. Beyond Antarctic circle the length of night is more than 24 hours in writer.
4. Arctic ocean lies in north of it.	4. Antarctica lies in south of it.

Identify the correct answers : 1 mark each

Question 1.
Lines of latitude are :
(a) circles of varying radii
(b) semicircles of equal length
(c) staright lines of varying length
(d) circles of same radius.
Answer:
(a) circles of varying radii

Question 2.
The zone between 23 \(\frac{1}{2}\)° N and 23 \(\frac{1}{2}\)° S is called the
(a) Temperate zone
(b) Torrid zone
(c) Polar zone
(d) Equatorial zone
Answer:
(b) Torrid zone

Question 3.
The Tropic of cancer refers to the line of latitude
(a) 0°
(b) 23 \(\frac{1}{2}\) S°
(c) 23 \(\frac{1}{2}\)N°
(d) 30° N.
Answer:
(c) 23 \(\frac{1}{2}\)N°

Question 4.
Latitude of a point is the angular distance of that point measured from
(a) North Pole
(b) Equator
(c) Prime Meridian
(d) South Pole
Answer:
(b) Equator

Question 5.
Lines of Latitudes are
(a) of equal length
(b) parallel to one another
(c) north to south lines
(d) coverage at the equator.
Answer:
(b) parallel to one another

Question 6.
The end points on the surface of the earth are called
(a) points
(b) dots
(c) poles
(d) tops
Answer:
(c) poles

Question 7.
Meridians are lines
(a) which coverage at the two poles
(b) which are of unequal length
(c) which are parallel
(d) which coverage at the equator
Answer:
(a) which coverage at the two poles

Question 8.
The parallels of latitude are
(a) triangular
(b) circular
(c) oval
(d) rectangular lines
Answer:
(b) circular

Question 9.
The parallel which is called the ‘Great Circle’
(a) 23° 30’N circle
(b) 0° circle
(c) 66° 30’N circle
(d) 90° circle
Answer:
(b) 0° circle

Question 10.
The Arctic circle is
(a) 23° 30’E
(b) 66° 30° N
(c) 66° 30° S
(d) 90° W
Answer:
(b) 66° 30° N

Fill in the blanks with correct words : 1 mark each

1. The _____ divides the earth into Northern Hemisphere and Southern Hemisphere.
Answer:
Equator

2. The distance between any two parallels of latitude is always _____.
Answer:
Equal

3. The _____ is also known as Zero Meridian.
Answer:
Prime meridian

4. The word ‘Meridian’ is derived from the Latin word Meridianus meaning _____.
Answer:
Mid-day

5. The parallel ____ degree south is called the Tropic of Capricorn.
Answer:
23 \(\frac{1}{2}\) S

6. The parallel ____ degree north is called the Arctic Circle.
Answer:
23 \(\frac{1}{2}\) N

If the sentence is true, write ‘T’ and if false write ‘F’ against the following : 1 mark each

1. The highest possible latitude is 360°.
Answer:
False

2. The equator divides the Earth into two equal halves.
Answer:
True

3. The Antarctic circle is the line of longitude as 66 \(\frac{1}{2}\)°N.
Answer:
False

4. The Tropic of capricorn lies in the Northern Hemisphere.
Answer:
False

5. The Prime Meridian is the reference line for locating places in an east-west direction.
Answer:
True

6. Latitude lines are of equal length.
Answer:
False

7. Longitude lines are also called meridiAnswer:
Answer:
True

8. Latitude of a place alone give us complete idea about the location of a place of the Earth surface.
Answer:
False

9. All meridians run in a east-west direction.
Answer:
False

10. The Earth axis makes 40° angle with the equatorial plane.
Answer:
False

11. The latitudes are semi-circles.
Answer:
False

12. All meridians are of equal length.
Answer:
True

13. There are two Frigid Zones on the Earth.
Answer:
True

14. Tempera-ture increases as we go away from equator.
Answer:
False

15. The Torrid Zone lies between the Tropic of cancer and Tropic of capricorn.
Answer:
True

Location of a Place on the Earth’s Surface Class 6 WBBSE Notes

Latitude and longitude : Lines of latitude and lines of longitude intersect each other to form a Grid. The Earth Grid helps in determining the location of a place.
Lines of latitude : These join the places of same latitude. These are called parallels of latitude as these are drawn parallel to the equator.
important parallels of latitude : Equator (0°), Tropic of Cancer (23 1/2° N), Tropic of Capricorn (23 1/2° S), Arctic circle (66 1/2° N), Antarctic circle (66 1/2° S) are important parallels of latitude.
Lines of Longitude: These are drawn from pole to pole. These are called meridians also 0° longitudeis called Prime meridian.

Time : Local time is time of the meridian of place i.e., 12 o’clock at noon. Standard time is the time of a central meridian of a country. Indian Standard Time (I.S.T.) is the time of 82 1/2° E Meridian near Allahabad, while G.M.T. is time of Greenwhich (0°. meridian) near London.

Time and longitude : There is a difference of 4 minutes for 1° of longitude. Eastern places are ahead of time. The following rule is used : East-Gain-Add. West-Lose-Subtract.

International Date Line : It is an imaginary line roughly corresponding to 180° meridian while crossing the international date line, ships gain or miss a day.

A globe is a model of the earth. Have you seen a globe in your school or home? It is a model of earth on a small scale. How do we locate places on the Earth ? The earth has no edges or corners which we can take as reference points or lines for measurement. For example, how do you locate your place in the classroom? Your seat may be the third seat in the second row. Here, you have two reference lines, namely the rows from the teacher’s table and number of seat from the entrance to the classroom. Therefore, we need two reference lines for locating places on the Earth.

The Equator and the Prime Meridian –

We know that the Earth is rotating on an imaginary axis.

The Poles : The two end points on the Earth’s surface at the top and at the bottom of the axis are called the poles of the Earth. That pole which points or ends towards the pole star is called the North Pole and the bottom end point is called the South Pole.

What is axis of the Earth?

An imaginary straight line joining the two poles (North and South Pole) passing through the centre of the Earth is called Earth’s axis. This axis is inclined to the plane of the earth’s orbit at an angle of 66 1/2°.

The Equator : If an east-west imaginary circle is drawn through the surface of the earth at an equal distance or midway from both the poles (north pole and south pole), it will divide the Earth’s surface into two almost equal halves. This imaginary line is called the Equator.

Hemispheres: The word hemisphere means half of a sphere i.e., the Earth. The e quat or divides the earth into two equal hemispheres. The northern half of the earth from the equator is known as the Northern Hemisphere and the southern half is known as Southern Hemisphere. So the half of the Earth to the north of the equator is called the Northern Hemisphere and half to the south of the equator is called the Southern Hemisphere.

All parallel circles from the equator upto the poles are called parallels of latitudes. These latitudes are measured in degrees. The equator itself is the largest among these lines (circles). The value of the equator is 0°. The remaining parallels become progressively smaller towards the poles. All the parallels are circular. The value of the north and the south poles of the Earth are 90° N and 90° S respectively.

Parallels of Latitudes: A line of latitude is an imaginary line on the Earth’s surface which joins all places having the same value to the north or south of the equator. The equator is the longest line of latitude. The length of equator is equal to the circumference of the Earth. Other lines of latitude are shorter length. The lengths of the lines of latitude decrease with distance from the equator. For example, 60° latitude is only half the length of the equator.

All lines of latitudes are circles parallel to the equator. Therefore, lines of latitude are called parallels of latitude.

Important parallels of latitudes –

Besides the equator and the two poles, the other important lines of latitude are the

• The parallel 23 1/2° N (North) is called the Tropic of cancer.
• The parallel of 66 1/2° N (North) is called the Arctic circle.
• The parallel 23 1/2° S (South) is called the Tropic of capricorn
• The parallel 66 1/2° S (South) is called the Antarctic circle.

The Tropics of cancer and capricorn mark the limits of the Tropical zone. In this zone, the Sun’s rays are overhead at least on one day in a year. The Arctic circle marks the limit of the North Polar Zone. The Antarctic circle marks the limit of the South Polar Zone. The Zone between the Tropic of cancer and the Arctic circle is called the North Temperate Zone. The zone between the Tropic of capricorn and the Antarctic circle is called the South Temperate Zone.

Based on latitude, we also describe different regions of the earth as under –

(a) Low Latitudes : The region between the Equator and 30° N or 30° S.
(b) Mid Latitudes : Between 30° and 60° N or S.
(c) High Latitudes : Between 60° and 90° N or S.

Relation between latitude and climate identification of Heat Zone:

Distance between the parallels of latitude : The circumference of the earth is 40,075 km. The parallels of latitude are all full circles. The circumference is 360°. So the distance between 1° latitude is therefore 40,075 ÷ 360 = 111 . 1 km (approx). Distance between the latitudes are not same always because of the earth’s shape. It is 110.56 km near equator ; 110.8 km at 30° latitude; 11.7 km at 89° latitude ; Average distance between the latitudes are 111 km (69 mile).

A Number of Latitudes : We know that there are 360° in a circle. From pole to pole it is only half a circle or 180°. So the number of parallels of latitude at an interval of 1° is 89 in the northern hemisphere and 89 in the southern hemisphere (as NRS poles are two dots). If we take equator ; then the total no. of parallel are 89 + 89 + 1 = 179.

Characteristics of latitudes or parallels of latitudes :

• All latitudes are full circles.
• The parallels of latitude run in the east west direction
• Parallels are always parallei to each other.
• Among the parallels the equatoi is the largest and knowri as Great Circle.
• As the latitude increases the circumference of the parallel decreases.
• Being parallel to each other they never intersects one another.
• All the parallels except North Pole and South Pole intersect meridians at right angles.
• The place lying on the same parallel receives almost the same heat but local time differs place to place.
• The maximum value of parallel is 90°.
• The total number of the parallels of latitude including equator is 89 + 1 + 89 = 179.

Longitude :

You will find that it is difficult to find the exact location with the help of latitude only. The latitude of New Delhi is 30° N. Then New Delhi can be any where along the latitude of 30° N. You need to know something else to fix its position. The other fixed line of reference is a line running from the North Pole to the Soth Pole, called the Prime Meridian. All other lines running from the North Pole to the South Pole are called meridians of longitude.

Longitude is the angular distance of a place east or west of the Prime Meridian (also called Zero Meridian or Fixed Meridian).

The distance between any two meridians is also measured in degrees. Since each meridian of longitude is a semi-circle running from the North Pole to the South Pole. The zone between the Prime Meridian and 180° E longitude is called the Eastern Hemisphere. The opposite zone (0° to 180° W) is called the Western Hemisphere.

All lines of longitude are semicircles of equal length. The distance or gap between two lines of longitude is maximum at the equator and decreases gradually away from the equator.

Characteristics of the Meridian of longitude :

• Longitude is the angular distance of a place east or west of the Prime Meridian.
• There are 360 meridians of longitude.
• The meridians are not parallel. They converge at the two poles.
• The meridians are semicircles.
• All the meridians are of equal length.
• The distance between any two meridian varies they get closer from the equator to the poles.
• All meridians run in a north south direction.
• All places on the same meridian have sunrise, sunset, noon, at the same times.
• Each meridian cuts the equator at right angle.

Great Circles: A great circle is a circle drawn on the Earth in such a way that the centre of the circle is the centre of the Earth. The radius of the great circle is the same as the radius of the Earth. A great circle is the largest possible circle that can be drawn on the surface of a sphere. Any number of great circles may be drawn on a sphere. All great circles divide the sphere any two equal hemisphere.

The equator is an example of a great circle. The equator divides the earth into two hemispheres. All lines of longitude are great circles. All lines of latitude except the equator are small cirles. The centres of the small circles are points other than the centre of the Earth. The small circles have radii which are smaller than that of the Earth.

Detailed explanations in West Bengal Board Class 6 Geography Book Solutions Chapter 2 Shape of The Earth offer valuable context and analysis.

WBBSE Class 6 Geography Chapter 2 Question Answer – Shape of The Earth

Objective Type Questions :

Question 1.
What is the shape of the Earth?
Answer:
An oblate spheroid.

Question 2.
What is the equatorial diameter of the Earth?
Answer:
12,757 km.

Question 3.
What is the polar diameter of the Earth?
Answer:
12,714 km.

Question 4.
Who was the first sailor to circumnavigate the Earth?
Answer:
Magellan.

Question 5.
Who was the first Greek philosopher to prove that Earth is spherical?
Answer:
Aristotle.

Question 6.
Who was the first scientist to prove that Earth is a spheroid?
Answer:
Newton.

Question 7.
Who was the first geographer who attempt to measure the size of the Earth?
Answer:
Eratosthenes.

Question 8.
Who was the first Indian Astronomer to describe the Earth as sphere?
Answer:
Aryabhatta

Question 9.
Which eclipse gives the evidence that the Earth is round?
Answer:
Lunar Eclipse.

Question 10.
What is the equatorial circumference of the Earth?
Answer:
40,077 km.

Question 11.
What is the polar cicumference of the Earth?
Answer:
40,009 km.

Question 12.
How much part of the Earth is covered with water?
Answer:
71%.

Question 13.
Which one of the earliest proofs of the Earth’s sphericity, is the most conclusive and practical?
Answer:
Shadow of the Earth at Lunar Eclipse.

Question 14.
What do you understand by the term ‘oblate spheroid’?
Answer:
A sphere with unequal diameter.

Question 15.
Which force creates a bulge at the equatorial region?
Answer:
Centrifulgal force.

Question 16.
Where is Bedford level canal located?
Answer:
In UK.

Question 17.
Who was the scientist to perform Bedford level canal experiment?
Answer:
A.R.Wallace.

Question 18.
What is the difference between polar diameter and equatorial diameter of the Earth?
Answer:
43 km.

Define and give very short answer of the following briefly 2 marks each

Question 1.
What is a spheroid ?
Answer:
A spheroid is not a perfect sphere. It is a sphere of rotation.

Question 2.
What is Geoid ?
Answer:
Geoid means Geo+oid. It means Earth shaped i.e., a spheroid.

Question 3.
What is centrifugal force ?
Answer:
A force which acts away from the centre of a circle.

Question 4.
What is Horizon ?
Answer:
Horizon is the line where Earth and sky seem to meet.

Question 5.
What do you mean by Geocentric?
Answer:
In olden days, it was believed that the Earth is the centre of Solar System.

Question 6.
What is heliocentric ?
Answer:
It means the idea that Sun is the centre of the Solar System.

Question 7.
What is circumnavigation ?
Answer:
To sail round the Earth without changing direction.

Question 8.
Explain the spherical hori-
Answer:
Where Earth and sky appear to meet. It always look spherical due to spherical Earth.

Question 9.
How does circumnavigation determine the Earth’s shape?
Answer:
Because it is possible to circumnavigate only the spherical Earth.

Question 10.
How do aerial photographs zon. help ?
Answer:
The photographs taken from space show spherical Earth.

Question 11.
Why is the shape of the Earth described as oblate spheroid?
Answer:
Because it is flattened at the poles and bulging at the equator.

Answer the following questions briefly : 3 marks each

Question 1.
Name the ancient Geographers and their views regarding shape of the Earth.
Answer:
In olden days, it was believed that the Earth is the centre of Solar System. To a common man, Earth appeared as a flat disc. Anaximander took it as cylindrical, Aristotle, Ptolemy, Aryabhatta and Pythagoras gave proofs that Earth is a sphere.

Question 2.
Name some modern Geographers and their views about shape of the Earth.
Answer:
(a) Magellan, after circumnavigation of the Earth, showed it to be a sphere.
(b) Copernicus proved that the Earth moved round the Sun.
(c) Galileo proved spherical shape of the Earth.
(d) Newton proved Earth to be a spheroid.

Question 3.
Why does the Sun not rise at the same time everywhere in the world?
Answer:
If the Earth were flat, the whole world would have the sunrise and sunset at the same time. As the Earth is spherical and rotates from West to East, places in the East see the Sun earlier than the places in the West.

Question 4.
“The whole of the approaching ship is not visible at one time.” Why ?
Answer:
Along its curved surface, the appearance of a ship is gradual. We see first the smoke, then the mast and then the hull. If the Earth were flat, the entire ship would be seen all at once.

Question 5.
How can you prove that the Earth is a shape by looking at the Pole Star ?
Answer:
The Pole Star is at an angle of 90° at the North Pole. Its angle decreases towards the equator. It can happen only in an arc of a circle on surface of a sphere.

Question 6.
Briefly describe the shape of the Earth.
Answer:
The Earth is not a perfect sphere. Due to its rotation on its axis, the shape of Earth is bulging at equator and flattened at poles. It is a spheroid.

Question 7.
How did Earth get its atmospheric blanket?
Answer:
From the rotating cloud of gas and dust, heavy elements were separated. The remaining cloud of gases formed the atmosphere and functions as a blanket.

Question 8.
“Even when the Earth is spherical, if appears to be flat.” Discuss.
Answer:
The actual shape of the Earth is spherical. The curvature of the Earth is small as compared to its big size. For a small area upto 100 sQuestion mile, this curvature is negligible. Therefore, it appears flat.

Question 9.
Why is the Earth slightly flattened at the poles ?
Answer:
The Earth is not a perfect sphere. It is slightly flattened at both the poles. It is due to the centripetal force produced by the rotation of the Earth.

Question 10.
Why does the Earth have an equatorial bulge?
Answer:
The rotation of the Earth produces centrifugal force acting outwardly on the surface of the Earth. Thus, the equatorial parts are pulled away from the centre. With the result, equatorial circumference is longer than the polar circumference by 125 km.

Question 11.
What is the latest and most convincing proof of the Earth’s spherical shape ?
Answer:
Photographs of the Earth have been taken by Apollo-astronauts from high altitudes. These give a true perspective view of the curvature from outer space. These show clearly the curved edge of the Earth. This is the most convincing proof.

Answer the following questions : 5 marks each

Question 1.
(a) Which Eclipse provides evidence to show a spherical Earth ?
(b) Who was the first scholar to provide this evidence?
(c) How did he prove that the Earth is a sphere ?
Answer:
(a) The lunar eclipse proves that the Earth is a sphere
(b) Aristotle was the first scholar to show this.
(c) The shadow cast by Earth on the Moon during the lunar eclipse is circular. Only a spherical Earth casts a circular shadow.

Question 2.
State four traditional proofs of the Earth’s spherical shape.
Answer:

1. The shadow cast by Earth on the Moon during a lunar eclipse is always circular.
2. The Sun, planets and other heavenly bodies are spherical in shape.
3. The Sun rises and sets at different times in different places due to curvature of the Earth.
4. Circumnavigation round the Earth is a proof of its spherical shape.

Question 3.
(a) Who was the first geographer to measure the circumference of the Earth ?
(b) What observations did he make?
(c) How did he calculate the circumference of the Earth?
Answer:
(a) In olden days, man was unable to determine the size of the Earth due to his limited knowledge. About 2000

years ago (in 230 BC) an Egyptian astronomer, Eratosthenes made the first attempt to measure the circumference of the Earth.

(b) He assumed that the Earth was a sphere. On 21st June, he observed at Syene (Aswan) in Egypt that the Sun was directly overhead at that place. At Alexandria, on the same day, the Sun was not directly overhead at noon. It was 7° 12 minute away from the vertical. Eratosthenes measured the distance between Syene and Alexandria. It was found to be 5000 stadia (925 km).

(c) Thus, assuming that the Earth’s circumference measured 360°, he calculated the circumference of the Earth.
7.2° angle on the circumference = 925 km
1° angle on the circumference = \(\frac{925 \times 10}{72}\) 360° angle on the circumference
= \(\frac{925 \times 10 \times 360}{72}\) = 46,250 km
This measurement was very close to the modern accurate measurement of 40,000 km.

Question 4.
Describe any three experiments to prove the Spherical Shape of the Earth.
Answer:
(i) If you observe a ship approaching sea coast, the top of the mast is seen first and the hull, lower parts are seen gradually. Due to the curvature of the Earth, the whole ship is not seen at one time.

(ii) Fix three poles of equal length at equal distance on the ground. These do not give a horizontal level. The top of the middle pole looks higher than the other two poles due to the curvature of the Earth. This experiment was done by Mr. A.R. Wallace on Bedford canal.

(iii) If you look around at the Earth’s horizon (where Earth and sky appear to meet), it will everywhere and always appear circular. It widens with increasing altitude due to Spherical Earth.

Question 5.
What is the shape of the Earth ?
Answer:
Nowadays, scientific knowledge and observations have proved that the Earth is spherical in shape. But the actual mea-
surements of Earth’s dimensions have revealed that Earth is not a perfect sphere. It is slightly bulging at the equator and flattened at both the poles. It is an oblate spheroid. Its equatorial diameter is longer than its polar diameter by 43 km.

Question 6.
What is ‘Geoid’ ?
Answer:
The Earth has a unique shape. It is not similar to anything. A special term ‘Geoid’ is used to describe the shape of the Earth. It means ‘Earth shaped’. It is a combination of two words (Geo+oid) and it means a shape identical to spheroid shape of the Earth.

Identify the correct answers 1 mark each

Question 1.
The average radius of the Earth is
(a) 5400 km
(b) 6,400 km
(c) 7,400 km
(d) 8,400 km
Answer:
(b) 6,400 km

Question 2.
The shape of the Earth is like the
(a) Cylinder
(b) Mango
(c) Pear
(d) Apple
Answer:
(c) Pear

Question 3.
Eratosthenes calculated the circumference of the Earth to be about.
(a) 1,52,000 stadia
(b) 2,52,000 stadia
(c) 3,52,000 stadia
(d) 4,52,000 stadia
Answer:
(b) 2,52,000 stadia

Question 4.
Greek philosopher and mathematician Pythagoras (572-500 B.C.) was among the first to suggest that the shape of the Earth was
(a) like a globle
(b) like a box
(c) like a cylinder
Answer:
(a) like a globe

Question 5.
From the space, the Earth looks
(a) black
(b) brown
(c) red
(d) blue
Answer:
(d) blue

Question 6.
During a lunar eclipse, the shadow of the Earth on the Moon appears as
(a) a straight line
(b) an arrow
(c) a box
(d) an arc of a circle
Answer:
(a) an arc of a circle

Question 7.
Due to sphere shape of the Earth, the Pole star at the North Pole can always be observed at
(a) 30° in the sky
(b) 60° in the sky
(c) 90° in the sky
(d) 180° in the sky
Answer:
(c) 90° in the sky

Question 8.
Megallan, the Portuguese explorer sailed completely around the Earth and returned to his starting point is
(a) Britain
(b) Spain
(c) Japan
(d) France
Answer:
(b) Spain

Question 9.
As one travels southwards, an angle of Pole star (North pole)
(a) increases
(b) decreases
(c) remains same
(d) becomes zero
Answer:
(d) decreases

Fill in the blanks with correct words 1 mark each

1. Polar circumference of the Earth is less than _______.
Answer:
Equator

2. The Earth bulges a little at the and is flattened at the _______.
Answer:
Equator

3. The shape of the Earth is described by scientists, have truely given the name ‘geoid’ meaning ‘_______’ or ‘_______’.
Answer:
Earth-shaped/Earth like form

4. During lunar eclipse shadow of _______ and its curvature can be observed with naked eye.
Answer:
Earth

5. The polar diameter of the Earth is _______.
Answer:
12,714 km

6. A Greek philosopher and scientist named _______ was the first to declare that the Earth is round.
Answer:
Aristotle

If the sentence is true, write ‘T’ and if false write ‘F’ against the following 1 mark each

1. If the earth was flat the pole star would have the same height for all latitudes.
Answer:
True

2. The height of the pole star in the sky varies with the latitude.
Answer:
True

3. When three ships are approaching the shore, the observer first see only one ship. The others lie below his line of vision.
Answer:
True

4. During an eclipse of the Moon, the shadow of the Earth which is thrown on the Moon, is always straight line.
Answer:
False

5. If the Earth was flat, the rising Sun would be seen at all places at the same time.
Answer:
True

6. Due to spherical shape of the Earth, places in the east see the rising Sun earlier.
Answer:
True

Shape of The Earth Class 6 WBBSE Notes

Earth : A unique planet. The Earth is a unique planet (Watery planet or Blue planet) because it is the only planet on which life exists.

Shape of the Earth : In olden days, people regarded the Earth as a plane surface, i.e., flat. But Anaximander, Aristotle, Ptolemy, Aryabhatta and Pythagoras gave proofs to show the Earth as a sphere.

Modern Views : Modern views confirm the spherical shape of the Earth, Magellan, Galileo, Copernicus, Newton proved the Earth to be a spheroid, i.e., a sphere of rotation. The Earth has the shape of Geoid. It is flattened at the poles and bulging at the equator.

Size of the Earth : An Egyptian Astronomer, Eratosthenes (230 BC) was the first to measure the size of the Earth. The equatorial diameter is 1,22,756 km. while polar diameter is 12,713 km.

In the old days, the Earth was considered to be a flat disc with steep edges. It was also thought that all heavenly bodies revolved around the earth. Early ideas of Universe were influenced by religious thoughts and practices. The Hindus believed that Universe was shaped like an egg-Brahmanda. According to Vedas, Earth was flat circular with a heaven above. Aryabhatta, the famous Indian astronomer, however, believed that the earth was spherical in shape and rotated on its axis. In Europe, the Greek philosopher Pythagoras was the first to state that the Earth was spherical in shape, there was considerable opposition to this idea in those days.

Nowadays, scientific knowledge and observations have proved that the Earth is spherical in shape. But the actual measurements of Earth’s dimensions have revealed that Earth is not a perfect sphere. It is slightly bulging at the equator and flattened at both the poles. It is an oblate spheroid.

The Earth is not flat –

If the Earth were a flat disc, then the rising Sun would have been seen at all places at the same time. This does not happen. Places in the east see the rising sun earlier.

When a ship approaches land, its funnel or mast is seen first and then the full. If the Earth had been flat, the whole ship would have been seen at one time.

The Earth is a sphere : Proof of sphericity of the Earth (How did we discovered the Earth is round?)
Several things show that the shape of the Earth is rounded or sphere.

Indirect Proofs –

Sunrise and Sunset : The Sun does not rise at the same time in every country. It rises in London, for example, some 5 hours later than in Mumbai. If the Earth were flat, the sunrise would be everywhere at the same time.

Sighting a ship : An observer watching through a telescope the approach of a ship seas first the smoke then the funnels, and then the hull. If the Earth were flat we would see the whole of the ship at one time. This proofs the rounded shape of the Earth.

The Earth’s shadow: The shadow cast by the Earth on the Moon during the lunar eclipse is circular. Only a round body can cast a circular shadow. All heavenly bodies like the Sun, Moon and other planets appear circular in all positions. The Earth and other heavenly bodies must be rounded and spherical in shape.

Travelling Round the Earth: As the Earth is spherical in shape, it is possible to circumnavigate the Earth. Magellan was the first to go round the Earth in a ship and complete his voyage without encountering a sharp edge. An aeroplane can fly round the world. If we travel continually in the same direction, we return eventually to our starting point.

The Bedfort Level

Experiment: An experiment was made many years ago in the Bedford Level Canal area in Britain. A.R. Wallace did this experiment. The water level of the canal provided the base of measurement. Three poles were fixed at intervals of about 5 km. such that the poles were rising to the same height about the level of water in the canal.

When a telescope was placed that in such a way that the top of pole A was in line with of pole C, it was found that the line of sight was intersecting the middle pole B. This would not happen if the Earth were flat. The middle pole B appeared higher owing to the curvature of the Earth.

The spherical horizon : The limit of the horizon at a place is circular and the horizon widens as the height of the observer increases. This again indicates the spherical shape of the Earth.

Effect of gravity : The weight of a substance is related to the effect of force of gravity on that substance. It is found that an object weighs nearly the same at all places on the Earth. This means that the force of gravity is nearly equal to all places. This is possible only when the Earth is a sphere.

Position of the pole star : The pole star appears vertically overhead at the North Pole. If the Earth were flat, the pole star should be overhead at all places on the Earth.

This is not the ease. The angle of elevation of the pole star is about 40° at London and 0° at Singapore or on equator. This is possible only when the earth is spherical in shape.

Direct Proofs –

Aerial Photographs : The most clinching evidence of the spherial shape of the Earth is obtained from photographs taken from space. Pictures taken by satellites show the spherical shape of the Earth. The astronauts from the moon have taken pictures of the Earth showing its spherical shape.

Artifical Satellites: Artificial Satellites and many space probes are put in orbit on the assumption that the Earth is spherical. The calculations have proved correct and the space probes of other planets of the Solar System have provided valuable data.

Earth as an Oblate Spheroid –

Definition of Oblateness of the Earth : A sphere which is slightly flattened at two opposite ends is called an oblate spheroid or oblate ellipsoid. The Earth is not, in fact, a perfect sphere, it has an equatorial bulge and a polar flattening. This type of spherical shape is known ‘oblate spheroid’.

Proofs of the Oblateness of the Earth –

Difference between the length of the Equatorial diameter and Polar diameter:

The Earth has got an equatorial diameter of 12,757 km. through east-west and a polar diameter of 12,714 km. through north-south. In length the equatorial diameter is larger than the polar diameter by 43 km. Hence there is a slight bulging at the equator and a flattening at the two polar regions. This is caused by the rotation of the Earth.

Length of circumferences : The length of equatorial circumference is 40,076 km and the polar circumference is 40,009 km. The legnth of equatorial circumference is larger than the polar circumference by 67 km. Thus the Earth has got a shape of an oblate spheriod.

Concept of Geoid : Earth is not a perfect sphere. It is also not a simple oblate spheroid. A study of satellite orbits has already revealed that the Earth is not a perfect oblate ellipsoid or a perfect sphere as it was previously thought to be.

The high mountains like Himalayas or deep valleys are also just a dot when we consider the size of the Earth. The Earth ‘bulges out’ a little at the equator and is flattened at the poles. There are much bigger depressions and bumps on its surface.

These are areas of low atmospheric pressure which produce climatic changes. In as much as Earth is unique, its shape is also unique. Scientists have truly given the name ‘geo’ to this form or ‘geoid’ meaning ‘earth like form’ or earth shaped.