WBBSE Class 10 Geography Solutions Chapter 1.2 Works of a River

Detailed explanations in West Bengal Board Class 10 Geography Book Solutions Chapter 1.2 Works of a River offer valuable context and analysis.

WBBSE Class 10 Geography Chapter 1.2 Question Answer – Works of a River

Answer in short : 2 Marks

Question 1.
What is the hydrological cycle?
Answer:
Water is present on the surface of the earth in rivers, lakes, oceans, ponds and other water bodies. This water gets evaporated by the sun’s heat and mixes with the atmosphere. Again, this vapour condenses and forms clouds and comes back to the earth’s surface as rain or snow. This cyclical movement of water from the earth’s surface and sub-surface to the atmosphere and vice versa is known as the hydrological cycle.

Question 2.
What is tributaries and distributeries ? Give example.
Answer:
Tributary : A tributary is a stream or a river which flows into a larger river. A tributary does not flow directly into a sea or ocean. For example, river Gomati and Son are tributaries of river Ganga.
Distributary : A stream that flows into a main-stream (or parent) river called distributary. For example, Hooghly is the distributary of Ganga.

Question 3.
What is peneplain?
Answer:
A more or less level land surface produced by erosion over a long period of time is called peneplain. It is a representation of a near-final stage of fluvial erosion. e.g.-Chotonagpur region.

Question 4.
What is Knick point ?
Answer:
Knick point refers to a particular point of the surface. where there is a sharp change in the slope of a river. After rejuvination, this particular point of sharp change of river slope occured, which is known as knick point.

Question 5.
What do you mean by rejuvination?
Answer:
The action of restoring a river or stream to a condition characteristic of a younger landscape is called rejuvination. Rejuvination occured for various reasons, i.e. earthquake, river captured etc.

Question 6.
What is a river ?
Answer:
A river is a flowing water body, which collects its water from rain and snow melt, flows down the hilly slopes through a natural channel due to gravitational force and meet with any other water body like ocean, sea, lake etc.

Question 7.
What is a river basin ?
Answer:
The area drained by the main river, the tributaries and distributaries from the source to the mouth is called the river basin.

Question 8.
What is a water-divide?

Answer:
The highland that separates two or more river basins lying adjacent to each other is called a water-divide. Usually the hills, mountains, ridges etc. act as waterdivides.

Question 9.
What is a river valley ?

Answer:
The channel through which a river flows, is known as the river valley. The shape and size of the river valley depends on the amount of water, depth of water and speed of the river.

Question 10.
What is an ideal river?
Answer:
An ideal river is one which has three prominent courses from source to mouth, i.e.- upper course or youth stage, middle course or maturity stage and lower course or old age stage.

Question 11.
Why is river Ganga known as an ideal river ?
Answer:
River Ganga is known as an ideal river because it exhibits all the three stages of a river. (i) The upper course lies from Gomukh to Haridwar, (ii) The middle course lies from Haridwar to Dhulian in West Bengal, (iii) The lower course lies from Dhulian to Gangasagar in West Bengal.

Question 12.
What is ‘Sixth power law’?
Answer:
The transportation capacity of a river depends on the river’s velocity and volume of water. If the velocity of the river is doubled, the transportation capacity is increased by 2⁶ = 64 times. This is known as the ‘Sixth power law’ of a river.

Question 13.
Name the methods by which a river erodes.
Answer:
A river erodes by the methods of – hydraulic action, corrosion or abrasion, attrition and solution.

Question 14.
Name the methods by which a river transports the eroded material.
Answer:
A river transports the eroded materials by – traction, saltation, suspension and solution processes.

Question 15.
Mention the factors on which the transportation capacity of a river depends.
Answer:
The transportation capacity of a river depends on – slope of the river valley, velocity of the river, volume of water, size, shape and characteristics of the loadbeing carried.

Question 16.
What is a pot hole ?

Answer:
The round pot-like holes cut on the river beds by the swirling water and the rock fragments by the process of corrosion or abrasion are called potholes.

Question 17.
What is a plunge pool ?
Answer:
The depression or hole created at the foot of a waterfall due to falling of water along with rock fragments with high velocity, is known as a plunge pool.

Question 18.
What is a cataract?
Answer:
When a series of waterfalls come down in steps over a staircase-like land form, it is known as a cataract.

Question 19.
What is a cascade?
Answer:
A series of small waterfalls of the same river lying close to each other is called a cascade.

Question 20.
What is a rapid ?
Answer:
When small streams or waterfalls come down with high velocity by jumping step by step over the area, it is called a rapid.

Question 21.
Name the different types of deltas.
Answer:
The different types of deltas are : Bird’s foot delta, Arcuate delta and Cuspate delta.

Question 22.
Give a brief introduction of the New Moore island.
Answer:
The newly formed island at the Indo-Bangladesh border, five kmsouth from the mouth of River Hariyabhanga in the Bay of Bengal, is known as the “New Moore’ or ‘Purbasha’ island.

Question 23.
What is a catchment area or catchment basin ?
Answer:
In the hilly regions, numerous small streams and springs of water flow from different directions and contribute the water to form a main river. These numerous thin streams and springs help to keep the supply of water continuously for the main river. This region, from the main river takes shape of a basin is called the catchment area or catchment basin.

Question 24.
What do you mea by ‘River regime’ ?
Answer:
According to F. J. Monkhouse, river regime refers to the seasonal variation of water volume in the river.

Question 25.
Mention the works done by a river in its course of flow.
Answer:
An ideal river has three stages in its course of flow. In the upper course, the river mainly erodes materials. In the middle course, the main work is transportation of the eroded load. In the lower course, the main work is deposition of the load transported so far.

Question 26.
What is ‘Cusec’ and ‘Cumec’?
Answer:
‘Cusec’ and ‘Cumec’ are units of measuring the volume of water flowing through a river. ‘Cusec’ refers to the amount of cubic feet of water flowing through a particular point of the river in one second time. ‘Cumec’ refers to the amount of cubic metres of water flowing through a particular point of the river in one second time.

Question 27.
What do you mean by the last limit of erosion of a river ?
Answer:
Last limit of erosion of a river refers to the last limit of the lower course of the river where its erosive power finally ends. Usually, the sea level is considered as the last limit of erosion of a river.

Question 28.
What do you mean by degradation by river ?
Answer:
In a river, if the load is lesser than the capacity of load that it can carry, it continues its work of erosion, thus lowering the river beds and widening the walls. This is known as degradation by river.

Question 29.
What do you mean by aggradation by river ?
Answer:
In a river, if the load is far more than the capacity of load that it can carry, it starts depositing the load, thus increasing the height of landforms and decreasing the depth of the river beds. This is known as the aggradation of river.

Question 30.
Name some important water-divides in India.
Answer:
The important water-divides present in India are :

1. The Himalayan range (the largest water-divide of India)
2. The Western Ghats (the second largest water-divide of India)
3. The Vindhya and Mahakal ranges (the third largest water-divide of India)
4. The Satpura range.

Question 31.
What is a ‘Fall line’?
Answer:
In a hilly region or a plateau region, when numerous small rivers flow towards a steep and almost vertical edge of a mountain ridge or plateau, a number of waterfalls are created in a line. This is known as a ‘Fall line’. Eg. – In North America, the Appalacian mountains meet the coastal plains in a steep slope, creating a series of waterfalls along the edge of the range.

Question 32.
Name the landforms created in the upper course of a river.
Answer:
The different landforms created in the upper course of a river are – V-shaped valleys, U-shaped valleys, gorges, canyons, waterfalls, plunge pools, pot holes, interlocking spurs etc.

Question 33.
Name the landforms created by deposition of rivers.
Answer:
The different landforms created in the lower course of a river are – alluvial cone, alluvial fan, flood plain, natural levee, meanders, sandbars, delta etc.

Question 34.
What is an arcuate delta?
Answer:
The deltas whose outer boundary lies in an arch or looks bow-shaped towards the sea are called arcuate deltas. Eg.- deltas of rivers Ganga, Nile, Hwang Ho etc.

Question 35.
What is a bird’s foot delta ?
Answer:

The deltas that look like a bird’s claws or fingers spreading one beside the other, are called Bird’s foot deltas. Eg. delta of river Mississippi in North America.

Question 36.
is a cuspate delta ?
Answer:

The deltas which have sharp edges towards the sea, and look like cusps or pointed teeth pointing towards the sea at the edge, are called cuspate deltas. Eg-deltas of rivers Tiber in Italy and Ebro in Spain.

Answer in brief : 3 Marks

Question 1.
When does a river start depositing its load ?
Answer:
The river starts depositing its load under the following conditions :
(a) If the volume of water in the river reduces due to less rainfall, drought, dry season or percolation through rock beds,
(b) If the slope of the river valley reduces, it also reduces the speed of the river.
(c) If load of the river increases.
(d) If the river flows through a lake for a certain length.

Question 2.
Differentiate between abrasion and attrition.
Answer:

Abrasion	Attrition
i. The river beds and walls get eroded by action of rock fragments hitting against them.	i. The rock fragments carried by the river hit against each other and reduce in size.
ii. Rock fragments collide against river beds and walls.	ii. Rock fragments collide against each other.
iii. This type of erosion is very effective.	iii. This type of erosion is less effective.
iv. This type of erosion creates pot holes, plunge pools etc.	iv. This type of erosion creates sand, silt, clay etc.
v. Depth and width of river channels increase.	v. Depth of river channel is reduced by certain deposition of silt or sand.
vi. Abrasion does not hinder transportation of materials by rivers.	vi. Attrition hinders transportation of materials to a certain extent.

Question 3.
Why are V-shaped valleys created in the upper course of rivers?
Answer:
The causes of formation of V-shaped valleys in the upper course of rivers are:

(a) The rivers have high velocity in the upper course. They cut downwards much more than sidewards. Thus the valleys look like a ‘V’.
(b) Sometimes the ‘I’ shaped valleys may collapse to form ‘V’ shaped valleys.
(c) The hard rocks of the river valley walls are difficult to erode by sidewise pressure of water than downward pressure.

Question 4.
Why is erosion predominant in the upper course of a river?
Answer:
Erosion is predominant in the upper course of a river as – (a) Steep slope of the region gives high velocity to the river and increases its erosive powers. (b) Volume of water remains high due to snow melt as well as rain water, which makes the river more active.

Question 5.
Differentiate between ‘Gorge’ and ‘Canyon’.
Answer:

Gorge	Canyon
i. Very narrow and deep valley created in hard rock mountainous regions.	i. Very narrow and deep valley created in soft rock arid and semiarid mountainous regions.
ii. Formed by down cutting of river much more compared to side cutting.	ii. Formed by down cutting of perennial rivers in arid regions, where side cutting is prevented due to lack of rainfall.
iii. Found in wet high fold mountain regions.	iii. Found in dry and arid regions and limestone regions as well.
iv. Resembles the alphabet ‘V’.	iv. Resembles the alphabet ‘I’
v. Eg. – Royal Gorge of Arkansas, Sampo Gorge of Tibet.	v. Eg. – Grand Canyon of the river Colorado, USA is the deepest canyon of the world.

Question 6.
Mention the conditions where a waterfall can be created.
Answer:
Water of a river falling freely from a certain height in the upper course of the river is called a waterfall. Waterfalls can be created by the following conditions:
(a) Hard and soft rock beds lying alternately horizontal, vertical or diagonal to each other.
(b) If a plateau meets a plain in a steep slope.
(c) Faulting across the river valley.
(d) Hanging valleys created by glacial action.
(e) Knick points created due to rejuvination of rivers.

Question 7.
Differentiate between alluvial cone and alluvial fan.
Answer:

Alluvial cone	Alluvial fan
i. When the river leaves the mountainous region and enters a region of less slope suddenly, it deposits its load like pebbles, sand, rock fragments etc. in the form of a cone. This is called an alluvial cone.	i. When water flows over the alluvial cones, the depositions of the cones get spread and looks like a halfcircle. This is known as an alluvial fan.
ii. This looks like a cone.	ii. This looks like a half-circle or a hand fan.
iii. Height of the cone is greater than the alluvial fan.	iii. Height of the fan is lower than the alluvial cone.
iv. Slope is steep.	iv. Slope is gentle.

Question 8.
Discuss briefly the different processes of transportation of load by a river.
Answer:
A river transports its load by the following processes:
(a) Traction : The heavier and large rock fragments are forced to flow down
along the river water by rolling on the floor of the river channel due to gravity.
(b) Saltation : The fragments of rocks are moved downstream by jumping over the river bed continuously.
(c) Suspension : The fine particles of the river’s load remain suspended in the river due to buoyancy of water while they are carried downstream.
(d) Solution : Soluble particles are dissolved in the river water and moved downstream.

Question 9.
What is a flood plain ?
Answer:

In the lower course, the speed of the river is much less due to very gentle slope of the land. The river starts depositing its load in the river bed itself, thus reducing its water holding capacity. During the rainy season, when excess water comes into the river, it overflows. Much of silt, sand and clay deposits also overflow with the water and spread over large areas. This process of repeated overflow and spread of silt develops an extensive plain on both sides of the river, known as flood plains.

Question 10.
What is a natural levee?
Answer:
When silt, clay etc, are deposited at the banks of a river in the middle course every year, the height of the banks are increased compared to the adjacent lands. This looks like a natural dam, and is known as a natural levee. Such features on either side of the river channel helps to increase the depth of the river bed and its water holding capacity.

Question 11.
Differentiate between the Catchment Area and River Basin.
Answer:

Catchment Area	River Basin
i. At the source of a river, numerous small streams and springs of water flow downwards from the surrounding highlands to supply water to the main river. This is known as the catchment area.	i. The main region through which the main river, tributaries and distributaries flow is known as the river basin.
ii. Main function of the catchment area is to supply water to the main river.	ii. Main function of the river basin is to collect water from rainfall and other tributaries and make it flow towards the sea.
iii. Catchment area lies only at the source of the river.	iii. River basin spreads after the catchment area till the mouth of the river.
iv. Catchment area is much smaller compared to the basin of the same river.	iv. River basin is many times larger than its own catchment area.

Question 12.
By what processes does the river erode in its course of flow ?
Answer:
A river erodes in the course of its flow by the following processes :

1. Hydraulic action : This is the process by which the river water itself exerts pressure and friction and causes erosion.
2. Corrosion : In this process the rock fragments and pebbles collide against the walls and floor of the river basin and cause erosion.
3. Attrition : The rock fragments and pebbles flowing in the river collide against each other and break into smaller fragments.
4. Cavitation : In a turbulent stream, numerous air bubbles are created. These bubbles exert severe pressure when they burst, thus can cause erosion.
5. Solution : Soluble materials may get dissolved in river water and get removed. This causes erosion.

Question 13.
On what factors does the transportation capacity of a river depend ?
Answer:
The transportation capacity of a river depends on the following factors :

1. Slope of land: Greater the slope of land, greater will be the velocity of the river, hence, greater will be the capacity of transportation.
2. Amount of water : Greater the amount of water, greater is the transporting capacity of a river.
3. Amount of load : Greater the amount of load, lesser is the transportation capacity.
4. Size and weight of load: Greater the size and weight of load, lesser is the transportation capacity.

Question 14.
On what factors does the erosive power of rivers depend?
Answer:
The erosive power of the rivers depend on the following factors :

1. Speed of the river: The speed of the river depends on the slope of the land. Higher the speed, greater the erosive capacity of the river.
2. Amount of water : Greater the amount of water present in a river, greater is its erosive power. It can be noted that in rainy seasons, when the water level of the rivers increases, their erosive powers also increase.
3. Nature of rocks in river bed : If the rocks of the river bed are soft in nature, the river will erode more. If the rocks are hard, erosion will be less.
4. River load: The amount of load carried by the river also influences erosive power of the river. Greater the amount of load, greater is the amount of erosion.

Question 15.
How are pot holes formed ?
Answer:

The river bed is much eroded by the rock fragments and pebbles being carried by the river itself. When these rock fragments hit constantly against the river bed, the softer rocks get eroded away, creating hollows or depressions. When water falls into these depressions, they swirl around and then move forward. These shallow depressions or hollows are called pot holes.

Question 16.
What is a meander?
Answer:

In the course of flow of a river, the speed of the river is much reduced from the middle course towards the lower course. This reduces the carrying capacity of the river. The river starts depositing materials within its own bed as well as the banks. Thus obstructions are created in the course of flow. To avoid these obstructions, the river starts taking curves gradually and elongates its course, so that all can be accommodated. These curved portions of the river are called meanders. Meanders may get intensely curved and cut off to form ox-bow lakes.

Question 17.
What is an ox-bow lake?
Answer:

In the middle and lower course of a river, the speed of the river reduces so much that the carrying capacity of the river also reduces. It starts depositing materials within its own bed as well as on the banks. Thus, the river starts taking curves, forming meanders. When these meanders take intense curves, they may get cut off from the main river due to depositions that block their way. The main river flows by in a straight path and the cut-off part remains stagnant, forming a lake. These lakes look like the foot of a horse or an ox. Hence, they are called ox-bow lakes.

Question 18.
What do you mean by river capture?
Answer:
When two streams are flow along a water divide, the stronger stream erodes faster and greater with the passage of time, the headward erosion of the stronger stream erode the water divider and flows instead down the bed of neighbouring weaker stream. This phenomena is called river capture. This can happen for several reasons, including earth movement, landslide or ice sheet sliding etc.

Question 19.
Classify deltas according to their origin and explain them.
Answer:
There are two types of deltas according to their origin, such as (A) Constructive and (B) Destructive deltas.
(A) Constructive delta : Rivers deposited all eroded materials (sand, silt etc) into its beds in the lower course and form triangled new land called delta. These deltas are also called constructive delta. Such as Majuli.
(B) Destructive delta : When these deltas are continuously changing their shape and size for the action of waves, and tides, they are called desctructive delta. Such as deltas of river Rhone

Question 20.
Why do floods occure frequently in the lower course of the river?
Answer:
Lower course of the rivers are prone to frequent floods. The reasons behind this are :
i. Surface slope is almost zero in the lower course of the river. So huge amount of water of the river can not able to flow with high velocity towards the sea.
ii. River beds are loaded with maximum deposits. Thus the depth of the river channel gradually decreases. During the rainy season, as the extra amount of water is added to the river, both the banks of the river get flooded.

Answer in details : 5 Marks

Question 1.
Describe the landforms created by erosion of river in the upper course.
Answer:
The various landforms formed in the upper course of the river are :

(a) Gorge or V-shaped valley : In the upper course, the down cutting force of the river is much more than lateral erosion. Hence, the channel develops more depth than width, and looks like a ‘V ‘ shaped valley.
(b) Canyan or I-shaped valley : When the river flows through an arid region made up of non-resistant rocks, most of its energy is spent in down-cutting rather than widening of the valley. Thus the valley developed looks like ‘I’ shaped.
(c) Pot holes : Round disc-like depressions curved by the swirling water and rock fragments on the bed or floor of the river are called pot holes.

(d) Waterfalls : When water of the river falls freely from a height due to very steep slope, it is called a waterfall. They are further classified into rapids, cataracts and cascades.

(e) Interlocking spurs : When a number of projecting ridges or spurs extend from opposite sides of the wall of a V-shaped valley alternately, they seem to overlap or interlock. Such a series of spurs are called interlocking spurs.

Question 2.
Discuss the landforms formed due to deposition in the middle course of a river.
Answer:

The landforms formed in the middle course of a river are :
(a) Alluvial cone : As the river descends from a mountain and enters into a plain, it deposits extra load at the foothills in the form of a cone. This is known as alluvial cone.
(b) Alluvial fan : When the alluvial cone spreads wider and looks like a half-wide or a hand fan, it is known as the alluvial fan.
(c) Flood plains : Flooding of the rivers spread silt and clay to extensive areas on both sides of the river channel. This forms the flood plains.

(d) Natural levee : Repeated flooding tends to increase the height of the river banks and looks like long extensive dams along the banks. This is called natural levee.
(e) Meanders : The river develops broad bends and ‘S’ curves while flowing through the depositions in the middle course. These are called meanders.

(f) Ox-bow lakes: When the curves of the meander comes too close, the loop tends to join, forming a neck. The curved portion of the loop is gradually cut-off by further deposition. This horse-shoe shaped stagnant water body is known as the ox-bow lake.

Question 3.
What is a delta ? Why do deltas develop at the mouth of the rivers?
Answer:
Velocity of the river is almost nil where it meets with the sea. Thus, the heaviest amount of depositions occur here. The main channel is broken into numerous distributaries as more and more depositions take place. The region acquires a triangular shape and looks like the Greek letter Delta (Δ), hence the name. Deltas develop under the following conditions :

(a) The sea bed near the mouth of the river is very shallow.
(b) Slope is negligible.
(c) Tidal action is low.
(d) Huge amount of bed load.
(e) Numerous tributaries of the main river to add up to the load.
(f) Low current of river water at the mouth.
(g) Wind blowing in opposite direction to the flow of river water.
(h) Enclosed sea with lesser disturbances.
(i) Long course of the river.
(j) Absence of lakes and other depressions in the path of the river.
(k) Wet and humid weather rather than dry weather.

Question 4.
Compare and contrast alluvial cone with delta.
Answer:

Alluvial cone	Delta
i. Formed due to deposition of materials at the foot hills of mountains when the river enters the plains from the mountains.	i. Formed due to heavy deposition of materials when the river tends to meet the sea at the lower course.
ii. Formed of coarse and bigger rock fragments deposited at the foot hills.	ii. Formed of very fine silt and clay particles deposited at the mouth of the river.
iii. Resembles a cone.	iii. Resembles a flat triangle area.
iv. Covers a smaller area.	iv. Covers a larger area.
v. No other classification.	v. Can be classified into bird’s foot, arcuate and cuspate deltas.

Multiple Choice Questions (MCQ) : 1 Mark

Question 1.
A river is a part of the – cycle.
(A) Hydrological
(B) Biological
(C) Ecological
(D) Atmosphere
Answer:
(A) Hydrological

Question 2.
The river attains water from
(A) Rainfall
(B) Snow melt
(C) Rain and show melt
(D) None of these
Answer:
(C) Rain and show melt

Question 3.
Qarrying and removing of loose bedrocks by running water of a river is known as
(A) Corrosion
(B) Hydraulic action
(C) Solution
(D) Attrition
Answer:
(B) Hydraulic action

Question 4.
The process of erosion by collision between flowing rocks and the river bed and walls is called
(A) Corrosion
(B) Traction
(C) Solution
(D) Attrition
Answer:
(A) Corrosion

Question 5.
Erosion of materials by dissolving in river water is called
(A) Abrasion
(B) Attrition
(C) Solution
(D) Saltation
Answer:
(C) Solution

Question 6.
Wearing down of rock materials by collision against each other is known as
(A) Attrition
(B) Solution
(C) Transportation
(D) Saltation
Answer:
(A) Attrition

Question 7.
Large rocks and pebbles are dragged by the river by the process of
(A) Transportation
(B) Traction
(C) Saltation
(D) Solution
Answer:
(B) Traction

Question 8.
Rock fragments move downstream by jumping continuously by the process of
(A) Siltation
(B) Saltation
(C) Solution
(D) Attrition
Answer:
(B) Saltation

Question 9.
Rock fragments remain suspended and are flown down by
(A) Solution
(B) Suspension
(C) Siltation
(D) Saltation
Answer:
(B) Suspension

Question 10.
Soluble particles are carried away by
(A) Saltation
(B) Corrosion
(C) Suspension
(D) Solution
Answer:
(B) Corrosion

Question 11.
The beginning of a river is called the
(A) Channel
(B) Silt
(C) Course
(D) Source
Answer:
(D) Source

Question 12.
The path of the river is called the
(A) Channel
(B) Bed
(C) Source
(D) Mouth
Answer:
(A) Channel

Question 13.
Small rivers joining the main river are called
(A) Tributaries
(B) Distributaries
(C) Source
(D) Mouth
Answer:
(A) Tributaries

Question 14.
Small streams that flow out of the main river are called
(A) Tributaries
(B) Source
(C) Distributaries
(D) Mouth
Answer:
(C) Distributaries

Question 15.
Two rivers meet at the –
(A) Mouth
(B) Source
(C) Confluence
(D) Channel
Answer:
(C) Confluence

Question 16.
A landform of the upper course of the river is
(A) Alluvial cone
(B) Canyon
(C) Meander
(D) Ox-bow lake
Answer:
(B) Canyon

Question 17.
Pot hole is created in the course of river.
(A) Lower
(B) Middle
(C) Upper
(D) Everywhere
Answer:
(C) Upper

Question 18.
Natural levee are formed in course of river.
(A) Upper
(B) Lower
(C) Middle
(D) Everywhere
Answer:
(C) Middle

Question 19.
Sand bars and deltas are formed in cource of river.
(A) Upper
(B) Lower
(C) Middle
(D) Everywhere
Answer:
(B) Lower

Question 20.
Materials deposited by rivers are called
(A) Moraine
(B) Debris
(C) Salts
(D) Alluvium
Answer:
(D) Alluvium

Question 21.
How much of the landform formation is influenced by the work of rivers?
(A) 30 %
(B) 50 %
(C) 60 %
(D) 70 %
Answer:
(D) 70 %

Question 22.
Who named the landform ‘delta’ for the first time?
(A) Herodotus
(B) Pithagoras
(C) Thornbury
(D) Davis
Answer:
(A) Herodotus

Question 23.
Which instrument is used to measure the water current of a river ?
(A) Barometer
(B) Altimeter
(C) Currentmeter
(D) Rain gauge
Answer:
(C) Currentmeter

Question 24.
An example of a water divide in India is
(A) Western ghats
(B) Punjab plains
(C) Eastern coastal plains
(D) Ganga plains
Answer:
(A) Western ghats

Question 25.
The delta of river – looks like the teeth of a saw.
(A) Nile
(B) Tiber
(C) Ganga
(D) Mississippi
Answer:
(B) Tiber

Question 26.
A bird’s foot delta is seen in the river
(A) Mississippi
(B) Ganga
(C) Nile
(D) Rhine
Answer:
(A) Mississippi

Question 27.
Potholes are created in the river channels due to
(A) Friction
(B) Abrasion
(C) Action of bubbles
(D) None of these
Answer:
(B) Abrasion

Question 28.
Canyons are created due to
(A) Erosion
(C) Deposition of rivers.
(B) Transportation
(D) Transportation and deposition
Answer:
(A) Erosion

Question 29.
The Majuli island is located in the river
(A) Ganga
(B) Brahmaputra
(C) Indus
(D) Narmada
Answer:
(B) Brahmaputra

Question 30.
The depressions created at the base of waterfalls are called –
(A) Potholes
(B) Plunge pools
(C) Alluvial fans
(D) Oxbow lakes
Answer:
(B) Plunge pools

Question 31.
The largest river basin of the world is
(A) Nile basin
(B) Ganga basin
(C) Amazon basin
(D) Rhine basin
Answer:
(C) Amazon basin

Question 32.
The water flowing through a river channel is measured in
(A) Knots
(B) Cm
(C) Cusec
(D) Inch
Answer:
(C) Cusec

Question 33.
The erosional work of the rivers depends on
(A) Channel gradient
(B) River load
(C) Velocity
(D) All of the above
Answer:
(D) All of the above

Question 34.
Which of the following involves removal of loosened materials of the rocks of valley walls and valley floors with the help of erosional tools?
(A) Solution
(B) Abrasion or Corrasion
(C) Attrition
(D) Traction
Answer:
(B) Abrasion or Corrasion

Question 35.
Which of the following is the mechanical tear and wear of the erosional tools in themselves?
(A) Traction
(B) Corrosion
(C) Abrasion
(D) Attrition
Answer:
(D) Attrition

Question 36.
The level at which a river completely stops erosional work is called
(A) Base level
(B) End level
(C) Maximum level
(D) Local level
Answer:
(A) Base level

Question 37.
A very deep and narrow valley is called a
(A) Gorge
(B) Canyon
(C) Pothole
(D) Plunge pool
Answer:
(B) Canyon

Question 38.
Which of the following may be defined as a vertical drop of water of enormous volume from a great height in the long profile of the river?
(A) Terraces
(B) Rapids
(C) Cataracts
(D) Waterfalls
Answer:
(B) Rapids

Question 39.
Alternate bands of hard and soft rocks give birth to a series of small step-like falls called
(A) Cataracts
(B) Rapids
(C) Cascades
(D) Terracas
Answer:
(C) Cascades

Question 40.
Which of the following refers to the bends in the longitudinal courses of the rivers?
(A) Waterfalls
(B) River terraces
(C) River meanders
(D) River valleys
Answer:
(C) River meanders

Question 41.
Which of the following is the result of both erosion and deposition?
(A) River valley
(B) River terraces
(C) Plunge pool
(D) Meanders
Answer:
(D) Meanders

Question 42.
The depositional features at the foot hills of the Himalayas are called
(A) Bhangar
(B) Bhabar
(C) Khadar
(D) None of these
Answer:
(B) Bhabar

Question 43.
Which of the deltas are formed when the river water is as dense as the sea water?
(A) Birdfoot delta
(B) Estuarine delta
(C) Arcuate delta
(D) Truncated delta
Answer:
(C) Arcuate delta

Question 44.
Ganga delta is an example of
(A) Arcuate delta
(B) Birdfoot delta
(C) Estuarine delta
(D) Truncated delta
Answer:
(A) Arcuate delta

Question 45.
Grand Canyon in United States is the work of river
(A) Colorado
(B) Mississippi
(C) Tennessee
(D) Missouri
Answer:
(A) Colorado

Question 46.
The longest river of the world is :
(A) Mississippi-Missouri
(B) Nile
(C) Ganga
(D) Amazon
Answer:
(B) Nile

Question 47.
‘Kuick point’ of a river is seen is
(A) Ox-bow
(B) Flood plain
(C) Waterfall
(D) Pot holes
Answer:
(C) Waterfall

Question 48.
Alluvial cones are formed in the rivers
(A) Upper
(B) Middle
(C) Lower course
(D) None
Answer:
(B) Middle

Question 49.
The river valley created in the dry regions due to deepcutting of soft rocks are called
(A) Gorge
(B) Canyon
(C) Hanging valley
(D) Creavasses
Answer:
(A) Gorge

Question 50.
The very deep and narrow ‘v’ shaped valley are called
(A) Gorge
(B) Canyon
(C) Interlocking Spur
(D) Waterfalls
Answer:
(B) Canyon

Question 51.
The unit for measuring the volume of water flowing through a certain part of a river is said to be 1 cusec, when the volume of water flowing through is
(A) 1 cubic meter
(B) 1 cubic feet
(C) 1 cubic inch
(D) 1 cubic centimeter
Answer:
(D) 1 cubic centimeter

Question 52.
When the speed of the river increase by two times, its carrying capacity increased by
(A) 7
(B) 2
(C) 3
(D) 64 times
Answer:
(D) 64 times

Question 53.
The main cause of submergence of the island of sundarbans is
(A) Heavy rainfall
(B) Cyclone
(C) Rise in sea level
(D) Flood
Answer:
(C) Rise in sea level

Question 54.
The sediments depositions on the convex side of meanders are called
(A) Pool
(B) Point bar
(C) Pluge pool
(D) flood plain.
Answer:
(B) Point bar

Question 55.
A falline is a
(A) Band of hard rocks
(B) Chain of waterfalls
(C) Steepness of valley side
(D) All of these
Answer:
(B) Chain of waterfalls

Fill in the blanks : 1 Mark

1. V-shaped river valleys are found in the ________ stage of the river.
2. The formation of rapids and waterfalls is found in the _______ course of the river.
3. The delta in Inda is the largest delta of the world.
4. The breaks in the channel gradient caused by rejuismation of rivers are called ________.
5. The average height of natural levees is ________.
6. If the speed of the river is doubled, its carrying capacity increases by _______ times.
7. The gersoppa waterfalls are also known as ________.
8. The _______ delta of India is an active delta.
9. River _______ is known as the sorrow of Bengal.
10. The waterfalls move _______ of the river.
11. The narrow plain region between two rivers is called the ________.
12. The landform which separates two river systems is called the ________.
13. _______ lakes are created near delta regions.
14. Deltas are created in the _______ course of rivers.
15. Alluvial fans are created at the _______ of mountains.
16. River _______ is an inland river of India.
17. The New Moore island is known as _______ in Bangladesh.
18. A fault lying across the river in a mountanious region gives rise to ________.
19. In the upper course of a river, downcutting of valleys mainly occure due to ________.
20. The longest river of the world is river _______.
21. The island of Newmoore and Ghoramara have submerged due to ________.
22. The river erodes least in the _______ course.
23. The term meander came from the river ________.
24. Holes formed by abrason on river bed are called _______.
25. According to the name of _______ river, the zigzag course of a river is as meander.
Amswer:
1. Youthful
2. Upper/Youthful
3. Ganga-Brahmaputra
4. Knick points
5. 10 m
6. 64
7. Jog falls
8. Sundarban
9. Damodar
10. Headward
11. Doab
12. Water divide
13. Oxbow
14. Lower
15. Foothill
16. Luni
17. South Talpatti
18. Waterfalls
19. Abreasion
20. Nile
21. Rise in the sea level
22. Lower
23. Buyuk meanders
24. Pot holes
25. Meanders.

State True or False : 1 Mark

1. Interlocking spurs are found in the lower course of the rivers. [ ]
2. If slope of land increases, the speed of river reduces. [ ]
3. No delta has developed at the mouth of river Narmada. [ ]
4. River Godavari is an ideal river. [ ]
5. River Brahmaputra is the longest river of India. [ ]
6. The river Ganga rises from the Chemuyung Dung glacier. [ ]
7. The New Moore is a newly formed island of the Sundarbans. [ ]
8. The process of friction of rock fragments with the river bed is called abrasion. [ ]
9. The middle course of the river Ganga lies between Allahabad and Patna. [ ]
10. Canyans are formed in cold climatic regions. [ ]
11. The rivers mostly erode sidewards in the upper course. [ ]
12. Meanders are created when the speed of the river increases. [ ]
13. River Ganga is a perenial river. [ ]
14. The mouths of the rivers are generally wide. [ ]
15. Deep creeks and estuaries are found in the Sundarban regions. [ ]
16. The plains formed at the base level of erosion by rivers has been termed peneplains by Davis. [ ]
17. The Dasam falls have been formed in the river Subarnarekha [ ]
18. ‘Meander’ comes from the river Menderes in Turkey. [ ]
19. The largest river island of the world is Ilha-da-Marajo. [ ]
20. The hairpin bend of a river is also called the ‘elbow of river capture’. [ ]
21. The main work of the river in its mountaneous course is erosion. [ ]
22. Work of river starts above the snowline. [ ]
23. Potholes are created in the riverbeds due to abrasion and attrition. [ ]
24. The sea level is the last limit of erosion. [ ]
25. The Grand Canyon lies in the course of river Colorado. [ ]
26. The scientific study of the river is known as potamology. [ ]
27. Rapids are larger than cascade in dimension. [ ]
28. Waterfalls are mostly formed at the upper stages of the rivers. [ ]
29. Oxbow lakes are seen in the upper course of a river. [ ]
30. Canyons are ‘U’ shaped valley. [ ]
31. Pot holes are formed at the base of waterfall. [ ]
32. The confluence of Alakananda and Bhagirathi rivers is at Devprayag. [ ]
Answer:
1. False
2. False
3. True
4. False
5. False
6. False
7. True
8. True
9. True
10. False
11. False
12. False
13. True
14. True
15 . True
16 . True
17. True
18. True
19. False
20. True
21. True
22. True
23. True
24. True
25. True
26. True
27. False
28. True
29. False
30. False
31. False
32. True

Match the following :

List 1	List 2
A. Arcuate delta	1. Mississippi delta
B. Birdfoot delta	2. Yellow river delta
C. Esturanine delta	3. Nile delta
D. Abandoned delta	4. Hudson delta

codes:

Answer:
[D]

Answer in few words : 1 Mark

Question 1.
What is a river?
Answer:
A large stream of flowing water along the slope on the earth’s surface.

Question 2.
What are the main works of a river?
Answer:
Erosion, Transportation, Deposition.

Question 3.
How many courses does an ideal river have ?
Answer:
Three courses – upper, middle, lower.

Question 4.
Where does a river start and end ?
Answer:
The river starts at the source and ends at the mouth.

Question 5.
What is a river basin ?
Answer:
The area drained by the main river, tributaries and distributaries.

Question 6.
Name some landforms of the upper course of the river.
Answer:
V-shaped and I-shaped valleys, gorges, canyons, pot holes, waterfalls etc.

Question 7.
Name some landforms of the middle course of the river.
Answer:
Alluvial cones and fans, flood plains, natural levee, meanders, ox-bow lakes etc.

Question 8.
Name some landforms of the lower course of the river.
Answer:
Sand bar, delta, braided channel etc.

Question 9.
Which is the largest delta of the world ?
Answer:
The Ganga-Brahmaputra delta.

Question 10.
Where was the Lohachara island situated ?
Answer:
Sundarban.

Question 11.
How far does the upper course of river Ganga lie?
Answer:
Gomukh to Haridwar.

Question 12.
On which course of the river depositional activities are the least?
Answer:
Upper course.

Question 13.
What is the curved of a river is called ?
Answer:
Meandar.

Question 14.
Name the place where the river meets the sea.
Answer:
Estuary.

Question 15.
What is the sediment carried by the river called ?
Answer:
Bed load.

Question 16.
Name the process of erosion in which air bubbles trapped in small spaces implode to erode rocks.
Answer:
Cavitation.

Question 17.
Which is the longest estuary of the world ?
Answer:
Gulf of Ob.