WBBSE Class 10 Geography Solutions Chapter 3 Hydrosphere

Detailed explanations in West Bengal Board Class 10 Geography Book Solutions Chapter 3 Hydrosphere offer valuable context and analysis.

WBBSE Class 10 Geography Chapter 3 Question Answer – Hydrosphere

Answer in short : 2 Marks

Question 1.
What are ocean currents?
Answer:

A continuous and regular horizontal movement of ocean water in a fairly defined direction over a great distance on the surface or sub-surface of the ocean is called ocean currents.

Question 2.
How many types of ocean currents are there?
Answer:
There are two types of ocean currents : warm current and cold current.

Question 3.
What is a Sargasso sea ?
Answer:
In the North Atlantic Ocean, the warm gulf current, the cold canary current and the warm north equatorial current flow in a circular pattern.
The water trapped in between these currents remains still and stagnant. A vast growth of moss and other small plants are seen here.This region is known as the Sargasso sea.

Question 4.
What are sand bars?
Answer:
When the warm and cold currents meet, the icebergs being carried by the cold current melts and the sand, pebbles etc. that were within the iceberg gets deposited at the base, creating sand bars. These are economically very useful, as low depth of the sea near the sand bars attract much fishes that are easily acquirable.

Question 5.
Mention two advantages of ocean currents.
Answer:
(i) Ocean currents help in navigation of ships.
(ii) A huge amount of planktons are available in the region where warm and cold currents meet. These attract huge amount of fishes and help in growing of fishing grounds.

Question 6.
Mention two disadvantages of ocean currents.
Answer:
(i) The meeting of warm and cold currents gives rise to huge amount of fog and may create stormy weather.
(ii) The icebergs that flow along with cold currents create a lot of trouble for sailing ships.

Question 7.
What is a tide?
Answer:
The sea water rises in the gulfs and at sea-coasts regularly twice a day at regular intervals. This periodic phenomena of alternate rise and fall in level of the seas is known as Tides.

Question 8.
Mention the causes of tides.
Answer:
The causes of tides are :

1. Gravitational pull of the moon.
2. Effect of Centrifugal force due to rotation of the earth.
3. Gravitational pull of the sun.

Question 9.
What are sea waves?
Answer:
The vertical movement of sea water due to force exerted by wind blowing on the surface, without any horizontal displacement of the water particles is called sea waves. In sea waves, the water moves only up and down.

Question 10.
What are the different controlling factors of ocean currents?
Answer:
The controlling factors of ocean currents are :
(i) Wind, (ii) rotation of the earth, (iii) temperature, density and salinity of ocean water and (iv) presence and location of landmasses.

Question 11.
How does wind cause ocean currents ?
Answer:
The planetary winds blowing over the oceans in fixed directions throughout the year are the main causes of ocean currents. The winds push the water of the oceans in particular directions creating currents. About 2-4% of wind energy is used to create ocean currents. Eg.- The monsoon winds control the flow of ocean currents in the Indian Ocean.

Question 12.
Which ocean shows seasonal reversal of ocean currents and why?
Answer:
The Indian Ocean shows seasonal reversal of ocean currents. Due to the commencement of monsoon winds, the ocean currents flow from south to north and during retreat of the monsoon winds the currents flow from north to south. Thus, there is a 180° reversal of flow of ocean currents during the season change.

Question 13.
What is an ‘Ice wall’?
Answer:
In the Atlantic ocean, near the islands of Newfoundland, the deep green water of the cold Labrador current coming from the north, pass the deep blue water of the warm gulf stream side by side. The boundary of these two currents can be seen very clearly, which looks like an ice wall.

Question 14.
Name two famous sand bars of the world.
Answer:
(i) Grand Bank near Newfoundland in North America.
(ii) Dogger’s Bank in the British Isles of England.

Question 15.
What is the gulf stream ?
Answer:

The part of the North Atlantic current that crosses the Carribean sea and Gulf of Mexico, is called the Gulf stream. It is a warm current (27°C) of deep blue waters.

Question 16.
What is the Grand Bank?
Answer:
Grand Bank is a huge sandbar created near Newfoundland in North America in the northwestern part of the Atlantic Ocean. It is about 96,000 sq . km. in area and its depth is less than 90 ~m. It is a famous fishing ground of the world.

Question 17.
What is the Labrador current?
Answer:

• Labrador current is the ocean current generated from the Arctic ocean due to the polar winds.
• This cold current flows along the western coast of Greenland (between Greenland and Canada) towards the south and flows further to the south along the eastern coast of Labrador Peninsula.

Question 18.
Name some important warm currents of the North Atlantic ocean.
Answer:
Some important warm currents of the North Atlantic Ocean are : (i) North Equatorial current, (ii) Carribean current, (iii) Gulf Stream, (iv) North Atlantic current, (v) Norway current etc.

Question 19.
Name some important cold currents of the North Atlantic Ocean.
Answer:
Some important cold currents of the North Atlantic ocean are : (i) Labrador current, (ii) Eastern Greenland current, (iii) Canary current, (iv) Arctic current etc.

Question 20.
Name some important warm currents of the South Atlantic Ocean.
Answer:
Some important warm currents of the South Atlantic Ocean are : (i) South Equatorial current, (ii) Brazil current, (iii) Guinea current etc.

Question 21.
Name some important cold currents of the South Atlantic Ocean.
Answer:
Some important cold currents of the South Atlantic Ocean are : (i) Antarctic current, (ii) Benguela current, (iii) Folkland current etc.

Question 22.
Name the different warm currents of the Pacific Ocean.
Answer:
Some warm currents of the Pacific ocean are : (i) East Australian current (ii) North and South Equatorial current (iii) Kuroshio current (iv) North Pacific current (v) Alaska current etc.

Question 23.
Name the different cold currents of the Pacific Ocean.
Answer:
The cold currents of the Pacific Ocean are : (i) Antarctic current (ii) Humbolt current (iii) California current (iv) Bering current (v) Kamchatka current etc.

Question 24.
Name some important warm currents of the Indian Ocean.
Answer:
Some important warm currents of the Indian Ocean are : (i) North Equatorial current (ii) South Equatorial current (iii) Madagascar current (iv) Agulhas current (v) Somali current etc.

Question 25.
Name some important cold currents of the Indian Ocean.
Answer:
Some important cold currents of the Indian Ocean are : (i) Antarctic Ocean current (ii) West Australian current etc.

Question 26.
Which currents meet near the Japan coast that helps in creation of fishing grounds?
Answer:
The warm Kuroshio current and the cold Kurile current meet near the coast of Japan, that helps in the formation of fishing grounds.

Question 27.
How does the temperature of ocean water influence the flow of ocean currents?
Answer:
Temperature of ocean water influences the flow and direction of ocean currents. The equatorial and tropical regions being warm, make the water of the adjacent ocean warm as well. The water remains lighter and tends to flow outward towards the poles. This vacuum thus created is filled up by incoming cold currents from the polar regions.

Question 28.
Why is the Japan coast prone to cyclones frequently?
Answer:
The meeting of the warm Kuroshio current and the cold Bering current are responsible for occurrence of frequent cyclones on the coast of Japan.

Question 29.
Why does the British Isles coastal region remain frost free while the Labrador coast remains frozen, inspite of both lying on the same latitude?
Answer:
The warm North Atlantic current flowing along the Western coast of the British Isles helps to keep the region frost free inspite of lying on the same high latitudes as the Labrador coast.

Question 30.
What is the importance of the warm gulf stream of the North Atlantic Ocean?
Answer:

1. The Gulf stream creates foggy conditions and storms near the coastal areas of Newfoundland.
2. It keeps the coastal regions of Norway and British Isles frost free.
3. It helps in creation of fishing grounds on the sandbar of Grand Bank near Newfoundland.
4. It helps in navigation and creation of ice walls.

Question 31.
What is a primary tide or Direct tide?
Answer:
The tide produced in front of the moon is called a Direct tide or Primary tide. Ocean water of the earth nearest to the moon are attracted more strongly. It happens when the moon is directly overhead and its strong attraction forces the water to pile up on that place to form high tide.

Question 32.
What is Secondary or Indirect tide?
Answer:
During high tide, piling of water takes place even at the antipode of the side facing direct tides. This is known as secondary or Indirect tide.

Question 33.
What is a Spring tide?
Answer:
Twice in a month, i.e. on New moon and Full moon days, the moon, the earth and the sun come in a straight line. The combined gravitational forces of the sun and moon cause the highest of high tides. This is called a Spring tide.

Question 34.
What is a Neap tide?
Answer:
When the sun and the moon lie at right angles to each other, the gravitational forces of both counteract each other. Thus the tidal range becomes comparatively low. This is called a Neap tide.

Question 35.
What is a Tidal Bore?
Answer:
When a tide enters the narrow and shallow estuary of a river, the front of the tidal wave appears to be vertical, owing to the piling up of water of the river against the tidal wave and friction against the river bed. The steep-nosed tide crest looks like a vertical water of water rushing upstream. This is called a Tidal Bore.

Question 36.
What causes the occurrence of Tidal Bores?
Answer:
Tidal bores may occur due to :

1. Funnel shape of the mouth of the river.
2. Presence of sandbars near the mouth of the river.
3. Tremendous current of the river water.

Question 37.
What is the interval between two high tides?
Answer:
The interval between two high tides is about 12 hours 24 minutes 44.5 seconds.

Question 38.
What is the interval between a high tide and a low tide ?
Answer:
The interval between a high tide and low tide is about 6 hours 12 minutes 22.25 seconds.

Answer in briefly : 3 Marks

Question 1.
Differentiate between waves and ocean currents.
Answer:

Waves	Ocean currents
i. This refers to the upward and downward movement of sea water.	i. This refers to the horizontal movement of sea water.
ii. The water moves up and down but no big displacement of the water occurs.	ii. The water flows through a specific path or direction horizontal to the surface of the sea.
iii. Created due to wind movement, vulcanism, earthquake etc.	iii. Created due to planetary winds, temperature of water, salinity, presence of landmass, rotational speed of the earth etc.
iv. Moves perpendicular to the alignment of coasts.	iv. Moves parallel to the alignment of coasts.
v. Useful for marine erosion and deposition.	v. Useful for carrying away the eroded materials.
vi. Does not influence weather and climate.	vi. Influences weather and climate.

Question 2.
How do prevailing winds influence ocean currents ?
Answer:
Ocean currents are mainly caused by prevailing winds. The planetary winds push the surface layers of ocean water towards a constant flow. If, due to seasonal change, the direction of wind is changed, the currents also have a similar change in their direction.
In Tropical regions, equatorial currents moves from east to west under the influence of trade winds. In Temperate regions, the westerlies drive the sea water from west to east.

Question 3.
What is the influence of difference in temperature of sea water on ocean currents?
Answer:
Temperature is low at the poles and high at the equator. The polar water is cool, heavy and sinks while the equatorial water is warm, light and floats. This sets up convectional currents in the ocean. Warm water of the equatorial regions are light and move along the surface towards the polar regions where they are cooled.

Question 4.
What is the influence of salinity of ocean water in formation of ocean currents?
Answer:
The salinity of ocean water varies from place to place. Water of high salinity are denser than water of low salinity. Hence water of low salinity flow on the surface while water of high salinity flows at the bottom towards water of low salinity.

Question 5.
How does the centrifugal force influence ocean currents?
Answer:
The centrifugal force at the equator is greater than that at the poles. Due to this variation of forces, the equatorial water moves towards the poles.

Question 6.
How does evaporation and rainfall influence ocean currents?
Answer:
Evaporation reduces the amount of water in the ocean and increases salinity. Rain water raises the sea level and reduces salinity. This difference between density of water caused by evaporation and rainfall helps to generate ocean currents.

Question 7.
How does the shape of the continents influence ocean currents ?
Answer:
The ocean currents generally follow the coastline of the continents while flowing. But presence of numerous islands in their way may bifurcate the currents into numerous smaller streams of ocean currents.

Question 8.
What are Primary and Secondary tides?
Answer:
The tides produced on the surface of the earth facing the moon are called primary tides or Direct tides. At the same time, there is a piling of ocean water on the antipode or the opposite side of the earth. These tides are called Secondary or Indirect tides.

Question 9.
What are spring tides?
Answer:
The term Spring tides comes from the German word ‘Springen’, which means to jump. Twice a month, at new moon and full moon, the sun, the earth and the moon fall in straight line. The combined gravitational pull of the sun and the moon causes the highest tides. These are known as Spring tides.

Question 10.
What are Neap tides?
Answer:
Neap tides occur when the sun and the moon lie at right angles to the earth. This happens in the first and last quarters of the moon. The gravitational force of the sun and the moon counteracts each other. The tidal range is neither too high nor too low. These tides are known as neap tides.

Question 11.
What is Syzygy?
Answer:
When the sun, the moon and the earth come along the same straight line, this fact is known as syzygy in astrology. Two types of positions are found in syzygy:
(i) Conjunction : At the time of Full Moon, when the earth comes between the moon and the sun in a straight line the position is called conjunction.
(ii) Opposition : At the time of New Moon, when the moon comes between the earth and the sun in the same line, this position is known as opposition.

Question 12.
What are Perigean tides and Apogean tides?
Answer:

Perigean tides : When the moon is the closest to the earth (354,330 km), this position is known as perigee. The perigee position increases the attracting force of the moon and the tide is extraordinarily high. This is known as Perigean tide.
Apogean tides : When the moon is farthest from the earth (4,03,320 km), this position is known as Apogee. Due to reduced attraction of the moon, the tide is also 20% less high. This is known as Apogean tide.

Question 13.
Mention the characteristics of ocean currents.
Answer:
The characteristics of ocean currents are :

1. The warm currents flow outwards from the equatorial region towards the polar region.
2. The cold currents flow inwards from the polar region to the equatorial region.
3. The ocean currents flow almost in the same direction as the direction of the prevailing winds.
4. Speed of ocean currents is higher in shallow water and slower in deep water.

Question 14.
How does the centrifugal force of the earth influence the creation of tides?
Answer:
Centrifugal force is generated due to the rotation of the earth. Due to this force, all particles tend to move outward in the opposite direction of the gravitational force. Thus, the water present on the earth’s surface always tends to rise and move in the opposite direction of gravitational force. This leads to the creation of tides in different parts of the earth.

Question 15.
Why high tides and low tides each occur twice a day ?
Answer:
The earth (each and every part) faces the moon after every 24 hours 49 minutes 29 seconds. The side that faces the moon experiences direct or primary high tides and the opposite side experiences indirect or secondary high tides. Again, as the earth rotates, the place which experienced primary high tide will now experience secondary high tide and vice versa. The time difference between primary and secondary tides is 12 hours 24 minutes 44.5 seconds. The places lying at right angles to places experiencing high tides will experience low tides. Hence, two low tides occur in each place. Thus we see that both high tides and low tides occur twice a day.

Answer in details : 5 Marks

Question 1.
Discuss the causes of ocean currents.
Answer:

The main causes of the origin of ocean currents are:
(a) Prevailing winds : The planetary winds or prevailing winds push the surface layers of the ocean water in front of them in a constant flow. If, due to a seasonal change, the direction of wind is changed, the currents also have a similar change in their direction. In Tropical areas, the equatorial currents moving along with trade wind move from east to west. In Temperate regions, westerlies drive the sea water from west to east.
(b) Difference in temperature: Temperature is low at the poles and high at the equator. The polar water is cool and becomes heavy and sinks. Te equatorial water is warm, light and floats. This creates a convectional current and the polar water move towards the equator and vice versa.
(c) Difference in salinity : The salinity of ocean water varies from place to place. Water of high salinity are denser than water of low salinity. Hence, water of low salinity flows on the surface while water of high salinity flows at the bottom of the oceans.
(d) Rotation of the earth : The rotation of the earth generates a centrifugal force, which causes generation of currents in the ocean water.
(e) Shape of coasts : The shape and direction of the coasts of the landmasses also change the direction of the currents.
(f) Centrifugal force : The centrifugal force of the earth is greater at the equator than the poles. Hence, water currents move from equatorial region to the poles.
(g) Evaporation and rainfall : Evaporation decreases water level and increases salinity while rainfall increases the water level and decreases salinity. This influences the flow of ocean currents.
(h) Melting of ice : Melting of ice raises the sea level and reduces salinity, influencing the ocean currents.

Question 2.
List the general characteristics of ocean currents.
Answer:
The characteristics of ocean currents are as follows:

1. The general movement of ocean currents is clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere.
2. Warm currents move towards cold seas and cold currents move towards warm seas.
3. In the lower latitudes, the warm currents flow on the eastern shores and cold currents in the western shores. This condition is reversed in the higher latitudes.
4. Convergence and divergence of warm and cold currents influence the direction of flow.
5. The shape and position of continents guide the direction of ocean currents.
6. The currents flow not only at the surface, but also below the sea surface.

Question 3.
What are the effects of ocean currents ?
Answer:
The various effects of ocean currents are:
i. Difference in temperature : The regions where warm ocean currents pass, become comparatively warmer, while the regions where cold ocean currents pass, become comparatively cooler.
ii. Rainfall : Winds crossing warm ocean currents gather enough moisture and cause much rainfall. But winds causing cold currents do not gather much moisture, hence do not cause much rainfall.
iii. Fog and Storms : Regions where warm and cold currents meet remain foggy almost throughout the year and often face storms.
iv. Parity in temperature: The ocean currents help to balance the distribution of heat of the water between higher and lower latitudes. Hence they influence distribution of world temperature.
v. Frost-free harbours : Warm currents help to keep the mouths of the harbours of higher latitudes frost-free even in winters.
vi. Navigation : Ships can move faster and easily along the ocean currents. Movement against the direction of currents is difficult, time consuming and fuel consuming.
vii. Sandbars : When warm and cold currents meet, the icebergs carried by cold currents melt. The sand, pebbles etc. being carried by the icebergs get deposited at the base, creating sandbars. These are economically useful as low depth of the sea in this region attracts much fishes which can be easily acquired.
viii. Business and commerce : Sandbars are good for growth of planktons, which are favourite fish foods. Thus huge number of fishes are attracted to these regions. This leads to a huge catch of fish, naturally leading to good business and commerce.

Question 4.
Discuss the causes of tides.
Answer:

The main causes of tides are –
i. Gravitational pull of the moon : Although both the sun and the moon exert gravitational force on the earth, the sun’s force is only 46 \% of that of the moon due to its large distance from the earth compared to the moon. Hence, the moon’s influence on the tides is twice as strong as that of the sun. The water of the earth nearest to the moon is pulled by its gravitational force. This makes the water on this side bulge, causing high tide. Waters on the opposite side also experience high tides at a comparatively lower scale. The areas perpendicular to these areas experience ebb or low tides.

ii. Effect of centrifugal force or rotation of the earth : Rotation of the earth causes generation of centrifugal force, which tends to throw the waters outwards. This causes the rise of water as tides.
iii. Gravitational pull of the sun : The sun also helps to cause tides. When it lies in the same side as the moon, it causes very big tides. When the sun lies in the opposite direction to the moon, it causes weaker tides.

Question 5.
Discuss the effects of tides.
Answer:
The various effects of tides are :

1. Tidal energy can be harnessed to generate electricity.
2. Fishermen’s activities are controlled by the rhythms of high and low tides.
3. Tidal water helps ships to move in and out of river ports.
4. Tides help to increase depth of channels, lower freezing points at river mouths, help to clear depositions at river mouths and clear sewage from large urban centres.
5. During high tides low lying areas along sea coasts are flooded and this water is trapped for production of salt.
6. Tides aid the destruction of coastline and help to move debris to the sea.
7. Bores are characteristics of certain river mouths, such as those of the Amazon, Colorado, Hooghly and Elbe.
8. When bores are well-developed, the moving wall of water may be 4-5 m high and is reported to be a terrifying and destructive phenomenon.

Question 6.
Why the time difference between two primary high tides of the same place is about 24 hours 49 minutes?
Answer:
The earth takes about 23 hours 56 minutes 48 seconds to complete one rotation. If the moon would have been fixed, the same place of the earth would have experienced primary high tides after every 23 hours 56 minutes 48 seconds. But as the moon is revolving in its orbit in 27 \(\)\frac{1}{3}\(\) days in the same direction due to earth’s rotation, the conditions change. As the speed of earth’s rotation and moon’s revolution are not the same the moon covers (360° ÷ 27 \(\)\frac{1}{3}\(\). day) = 13° 10′ 14.63″ angular distance every day. Therefore, the moon takes extra time of (13° 10’14.63″ × 4. minutes) = 52 minutes 41 seconds to reach the same place once again. For this, the time difference of primary high tides at a particular place of two following days is about 24 hours 49 minutes 29 seconds.

Multiple Choice Questions (MCQ) 1 Mark

Question 1.
Water movement is –
(A) Vertical
(B) Horizontal
(C) Vertical and horizontal
(D) None of these
Answer :
(B) Horizontal

Question 2.
Waves are caused due to –
(A) Winds
(B) The moon and the sun
(C) Tides
(D) Ocean currents
Answer :
(A) Winds

Question 3.
On the new moon, occurs the –
(A) Spring tide
(B) Neap tide
(C) Ebb tide
(D) Low tide
Answer :
(A) Spring tide

Question 4.
Warm ocean currents flow towards the –
(A) Polar regions
(B) Equatorial regions
(C) Tropical regions
(D) Temperate regions
Answer :
(A) Polar regions

Question 5.
At the places where warm and cold currents meet, occurs –
(A) Cyclones
(B) Tides
(C) Clear sky
(D) Dense fog
Answer :
(D) Dense fog

Question 6.
Cold water is seen in –
(A) Pacific Ocean
(B) Atlantic ocean
(C) Indian ocean
(D) Arctic ocean
Answer :
(B) Atlantic ocean

Question 7.
Warm currents flow along the –
(A) Low latitudinal or Equatorial region
(B) Middle latitudinal region
(C) High latitudinal region
(D) Polar region
Answer :
(A) Low latitudinal or Equatorial region

Question 8.
The El-Nino which influences the Indian monsoon is –
(A) A cold ocean current that flows northwards along the coast of Chile
(B) A warm ocean current that flows westwards
(C) A low pressure system over western coast of Spain
(D) None of these
Answer :
(D) None of these

Question 9.
What is the interval between high tides at a place ?
(A) 12 hour
(B) 12 hour 26 minute
(C) 15 hour 30 minute
(D) 24 hour
Answer :
(B) 12 hour 26 minute

Question 10.
The place lying opposite to the moon experiences –
(A) Low tide
(B) Primary tide
(C) Secondary tide
(D) No tide
Answer :
(C) Secondary tide

Question 11.
Neap tide occurs on the – day after the new moon and full moon.
(A) 5 th
(B) 6th
(C) 7 th
(D) 8 th
Answer :
(D) 8 th

Question 12.
The South and North Equatorial currents of Atlantic Ocean move from east to west by the influence of –
(A) Trade winds
(B) Westerlies
(C) Polar winds
(D) Local winds
Answer :
(A) Trade winds

Question 13.
The direction of ocean currents is reversed with seasons in the –
(A) Pacific Ocean
(B) Atlantic Ocean
(C) Indian Ocean
(D) Arctic Ocean
Answer :
(C) Indian Ocean

Question 14.
Average salt content in 1 litre of sea water is –
(A) 39 gm
(B) 37 gm
(C) 35 gm
(D) 32 gm
Answer :
(C) 35 gm

Question 15.
The water in the oceans move horizontally over vast areas due to –
(A) Slope of the sea floor
(B) Waves
(C) Difference in density
(D) Currents
Answer :
(C) Difference in density

Question 16.
The tide at its maximum height is known as –
(A) Primary tide
(B) Neap tide
(C) Spring tide
(D) Ebb tide
Answer :
(C) Spring tide

Question 17.
The factors responsible for the movement of the surface oceanic currents are –
(i) Prevailing winds
(ii) Earth’s rotation
(iii) Earth quake
(iv) Difference in density of sea water
(v) Sea floor topography
(A) i, iii and iv
(B) i, ii and iii
(C) i, iii and iv
(D) None of these
Answer :
(A) i, iii and iv

Question 18.
Dense fog is formed near Newfoundland and Grand Bank due to convergence of –
(A) Cold Labrador current and warm gulf stream
(B) Cold Canary current and warm gulf stream
(C) Cold Labrador current and warm kuroshio current
(D) None of these
Answer :
(A) Cold Labrador current and warm gulf stream

Question 19.
The position of smallest distance between the earth and the moon is called –
(A) Apogee
(B) Perigee
(C) Apogean
(D) None of these
Answer :
(B) Perigee

Question 20.
High tides are caused when –
(A) The sun, earth and moon lie in a straight line.
(B) The sun and moon lie perpendicular to the earth
(C) Both ‘A’ and ‘B’
(D) None of these
Answer :
(A) The sun, earth and moon lie in a straight line.

Question 21.
High tides are caused at the time of-
(A) Fullmoon
(B) New moon
(C) Both ‘A’ and ‘B’
(D) None of these
Answer :
(C) Both ‘A’ and ‘B’

Question 22.
High tides are also called –
(A) Neap tides
(B) Spring tides
(C) Ebb tides
(D) Primary tides
Answer :
(B) Spring tides

Question 23.
The sun, the moon and the earth are in position of opposition during the-
(A) New moon
(B) Full moon
(C) Half moon
(D) Crescent moon
Answer :
(B) Full moon

Question 24.
The position of the sun, moon and earth in a straight line is called-
(A) Syzygy
(B) Quadrature
(C) Opposition
(D) None of these
Answer :
(A) Syzygy

Question 25.
When the earth lies inbetween the sun and the moon, the position is called –
(A) Conjunction
(B) Opposition
(C) Quadrature
(D) None of these
Answer :
(B) Opposition

Question 26.
When the sun, earth and moon lie in a position of right angle, it is called-
(A) Opposition
(B) Conjunction
(C) Quadrature
(D) None of these
Answer :
(C) Quadrature

Question 27.
During neap tides, the sun, earth and moon come in the position of-
(A) Opposition
(B) Quadrature
(C) Syzygy
(D) Conjunction
Answer :
(B) Quadrature

Question 28.
The position of farthest distance between earth and moon is called –
(A) Apogee
(B) Perigee
(C) Conjunction
(D) Opposition
Answer :
(A) Apogee

Question 29.
Cold wall is seen in
(A) Atlantic
(B) Antractic
(C) Indian
(D) Pacific Ocean
Answer :
(A) Atlantic

Question 30.
Which of the following is an warm current ?
(A) Kamchatka
(B) Peru
(C) Brazil
(D) West Australian
Answer :
(C) Brazil

Question 31.
Ocean currents are generated due to
(A) Difference in temparature
(B) Difference in Salinity
(C) Movements of Planetary winds
(D) All the above is correct
Answer :
(C) Movements of Planetary winds

Question 32.
The speed of ocean current in shallow seas compared to deep seas is
(A) More
(B) Less
(C) Not affected
(D) Remain same
Answer :
(A) More

Question 33.
Grand bank is a
(A) Warm Current
(B) Cold Current
(C) Submerged bar
(D) Island
Answer :
(C) Submerged bar

Question 34.
Ocean currents created by
(A) Rotation of the earth
(B) revolution of the earth
(C) Gravitational force
(D) None of these
Answer :
(A) Rotation of the earth

Fill in the blanks : 1 Mark

1. The general movement of a mass of oceanic water in a definite direction is called ________.
2. Okhotsk current is found in the _________ ocean.
3. _______ currents help in the formation of Sargasso sea.
4. _________ current is characterised by high temperature and high salinity.
5. ________ current is also known as Humboldt current.
6. North-east monsoon currents are produced between Andaman and ________.
7. El-Nino is a weather event restricted to certain ________ areas.
8. El-Nino maximum affects the ________ coast.
9. Fall of sea water and its movement towards the sea is called an ________.
10. Each day, tide is delayed by _______ minutes.
11. Perigean tides are ________ percent higher than the normal tides.
12. The coasts of British Isles and Norway remain frost-free due to the influence of the _______ current.
13. The _______ winds control the currents of the Indian Ocean.
14. The largest sand bar of the world is the ________.
15. The Madagascar and Mozambique currents combine to form the ________ current.
16. The warm _________ current keeps the east coast of Japan warm in winter.
17. ________ is created at the meeting points of warm and cold currents.
18. Heavy saline water flows as ________.
19. The average speed of ocean current is ________.
20. ________ is the largest ocean of the world.
21. The colour of water in the ________ current is slightly greenish.
22. The floating blocks of ice in the ocean are called ________.
23. The ice wall can be seen in the _______ Ocean.
24. The Sargasso Sea has been created in the _______ Ocean.
25. Planktons concentrate where ________.
Answer:
1. Ocean current
2. Pacific
3. Artiles
4. Brazil
5. Peru
6. Somali
7. Tropical
8. Peruvian
9. Ebb
10. 26
11. 15-20
12. Warm gulf stream
13. Monsoon
14. Grand Bank
15. Aguthas
16. Kuroshio
17. Fog
18. Under current
19. 5-10 km/ hr.
20. Pacific Ocean
21. Labrador
22. Ice bergs
23. Atlantic
24. Atlantic
25. Warm and Cold Currents meet

State True or False : 1 Mark

1. Benguela current flows through the Indian Ocean. [ ]
2. The ocean curents get deflected due to coriolis force. [ ]
3. The cold oyashio current flows along the coast of Japan. [ ]
4. Grand Bank lies in the Pacific Ocean. [ ]
5. Meeting of warm and cold ocean currents lead to the formation of fog. [ ]
6. Bering current is a cold current in the North Pacific Ocean. [ ]
7. Labrador current is a cold current in the North Atlantic Ocean. [ ]
8. A warm current flowing through the south Pacific Ocean is the New South Wales current. [ ]
9. A cold current flowing through the South Pacific Ocean is the Peru current. [ ]
10. The rising and falling of ocean water is known as ocean current. [ ]
11. The Humboldt current follows the coast of Chile. [ ]
12. The warm gulf stream lowers the temperature of the Eastern coast of North America in winter. [ ]
13. The meeting of the warm Kuroshio current and the cold Oyashio current lead to formation of dense fog and stormy conditions along the Japan coast. [ ]
14. The Western coast of the continents in tropical regions are influenced by cold curents, which lead to lack of rainfall and formation of deserts. [ ]
15. Ebb tides occur on new moon and full moon nights. [ ]
16. Tidal bores occur in the lower course of the river Hugli. [ ]
17. The ocean currents in the southern hemisphere are deflected towards the left due to rotation of the earth. [ ]
18. The Sargasso sea has no current. [ ]
19. Kuroshio current is a warm current. [ ]
20. California current is a cold current. [ ]
21. Foggy weather persist near the cold wall. [ ]
22. Drought occure along the east coast of Pacific ocean under the influence of La Nina. [ ]
Answer:
1. False
2. True
3. True
4. False
5. True
6. True
7. True
8. True
9. True
10. False
11. True
12. False
13. True
14. True
15. False
16. True
17. True
18. True
19. True
20. True
21. True
22. True

Answer in few words : 1 Mark

Question 1.
How much of the earth’s surface is covered by oceans?
Answer:
About 3 / 4 th.

Question 2.
What is the tide caused on full moon called ?
Answer:
Spring tide.

Question 3.
Which ocean currents move towards polar regions ?
Answer:
Warm ocean currents.

Question 4.
What type of ocean currents originate in high latitudes?
Answer:
Cold currents.

Question 5.
Which ocean currents have lighter water ?
Answer:
Warm currents.

Question 6.
Which ocean currents have denser water?
Answer:
Cold currents.

Question 7.
What is the direction of flow of ocean currents in the northern hemisphere?
Answer:
Clockwise.

Question 8.
What is the other name of Low tide?
Answer:
Ebb tide.

Question 9.
How many tides occur in a day?
Answer:
Two high tides and two low tides.

Question 10.
What is the upward and downward movement of ocean water called?
Answer:
Ocean waves.

Question 11.
Which is the main controlling power of the ocean current?
Answer:
Planetary wind.

Question 12.
In which ocean Sargasso sea is seen ?
Answer:
Atlantic ocean.