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Question A.1:

What is gradation? What are the two types of forces that bring about gradation?

Answer:

The breaking down, transportation and deposition of rock minerals leading to the levelling of the Earth's surface is known as gradation. 

The two forces that bring about gradation are as follows:
  1. Internal forces: These are the forces that act from within the Earth's surface. For example, volcanos and earthquakes
  2. External forces: Such forces act over the Earth's surface. For example, winds and waves

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Question A.2:

What is weathering?

Answer:

Weathering is a process in which huge rocks are broken down or decomposed into fine material. Several forces are responsible for this process. The most common agents of weathering are plants, animals and winds. 

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Question A.3:

What is a gorge? Give an example.

Answer:

A gorge is an I-shaped, narrow and deep valley formed by a river when it erodes the rocks vertically. Indus and Brahmaputra rivers form deep gorges when they cut across the Himalayan ranges.

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Question A.4:

How is a waterfall formed?

Answer:

Waterfalls are an example of spectacular landforms formed by the rivers in mountains. They are formed in two ways:
  1. When the slope of a river bed drops down all of a sudden, the water plunges down from the mountain in the form of a magnificent waterfall.
  2. Faulting may also result into a break in the land surface and hence, the slope of the river bed drops and results into waterfall.

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Question A.5:

What is a delta? Name the biggest delta in the world.

Answer:

Delta is a triangular landform that a river forms near its mouth (where it meets the ocean or sea). Since the river deposits most of its sediments near the mouth, these deposited sediments force the river to split into several distributaries and this region is collectively known as Delta. 

The Ganga-Brahmaputra Delta is the biggest delta in the world.

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Question A.6:

What are moraines?

Answer:

The rock material deposited alongside the valley due to the melting of glaciers is known as moraine or glacial moraine. It is composed of debris varying in size, ranging from fine silt to large stones or boulders.

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Question A.7:

What are mushroom rocks?

Answer:

Due to the action of strong winds carrying dust particles, sand and gravel, the erosion of rocks takes place. Since the wind is unable to carry dust particles at great height, it erodes the lower part of rocks more than the upper part. This results into a relatively narrow base and extensive top of the rocks, resembling the shape of a mushroom. Hence, these rocks are known as mushroom rocks.

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Question A.8:

How is a sand dune formed?

Answer:

Sand dunes are formed when an obstacle comes in the path of the movement of sand-carrying winds. The coarse sand particles get deposited in the form of a hillock or mound with its windward side as gentle and leeward side as steep. Sand dunes vary in height, ranging from few metres to several hundred metres.

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Question A.9:

What are lagoons? Give an example?

Answer:

Lagoon is a very common coastal feature found all over the world. It is formed when a shallow water body is separated from sea water or any large water body by a small land mass, resulting in the formation of a relief feature that resembles a partially enclosed lake.

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Question A.10:

Name two sea beaches of India.

Answer:

Beaches are formed when tides leave sand, gravel and pebbles on the shore and they get deposited over a long period of time. India has an incredibly long coastline and hence, there are large number of beautiful beaches in the country.

Following are the names of two beaches of India:

  1. Kovalam beach: It is a white, sandy beach on the Malabar coast in Kerala.

  2. Varca beach: It is a long strip of land in Goa with quiet and calm atmosphere.   

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Question B.1:

Degradation and aggradation

Answer:

The process of levelling of the surface of the Earth is known as gradation. This results from a range of factors like waves, glaciers and running water. These factors are cumulatively referred as agents of gradation. 

Degradation is the process of reduction in height of various landforms resulting from the action of several agents of gradation by breaking down the rocks into small fragments. Aggradation, on the other hand, is the increase in height of a landform that results from the deposition of rock fragments in low lying areas. 

Hence both these processes maintain balance of the Earth's surface.
 

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Question B.2:

Weathering and erosion

Answer:

Weathering Erosion
Weathering is the process of decomposition of rocks resulting from the loosening of rock particles. When the disintegrated particles formed due to weathering start moving from one place to another then it is known as erosion.
There are several agents of weathering like heat, cold, chemical factors and water. Agents responsible for erosion and deposition of particles from one place to another are glaciers, sea waves, running water, wind, etc.
This process does not involve the movement of particles form one place to another. The second stage of weathering is known as erosion (the movement of particles and their deposition).
No new landform is created as a result of weathering. New landforms are created due to erosion, for example, sand dunes.

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Question B.3:

Tributary and distributary

Answer:

Tributaries and distributaries are streams of fresh water bodies varying in their direction of flow. Tributaries are  small streams of water that join the mainstream river to increase its water supply. They originate from glaciers, lakes and underground water streams. They join the river during its course mostly in its middle and younger stage. Distributaries, on the other hand,  occur as a result of branching of a river near its mouth at a low-lying delta region. River carries a huge amount of silt and gravel at it mouth and this enhanced volume results into the branching of the river from it main channel. These streams are known as distributaries.

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Question C.1:

A river flows very slowly as it approaches the sea.

Answer:

The place where a river meets the sea or any other water body is known as its mouthBy the time the river reaches its mouth, it is carrying with it a large amount of silt, alluvium and water that reduces its speed.

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Question C.2:

Wind erosion is more prominent in the deserts.

Answer:

Winds that carry with themselves a huge amount of sand, dust particles and gravel are a strong agent of erosion. Deserts, due to lack of vegetation, are more prone to erosion. The absence of vegetation, which holds the land firmly, results in the sand laying loose that causes the erosion.

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Question D.1:

Describe the landforms formed by a river in the plains.

Answer:

Major landforms formed by a river in plains are as follows:

1. Meanders: When the river enters the plain, it losses it swiftness and the valley widens due to the continuos erosion of banks of the river. The river makes several bends along its flow and these bends and loops are termed as meanders.

2. Ox-bow lakes: As a result of continuos flow of the river, in the long run, the bends and loops come closer and with time, the river cuts across the loops separating them from the mainstream. These circular loops that get separated from the mainstream are termed as ox-bow lakes.

3. Flood plains: During floods, rivers bring with them a huge amount of silt and alluvium that gets deposited along the bank of rivers raising their height and forming fertile flood plains.

4. Natural levees​: Long ridges with relatively lesser height formed at the bank of rivers are termed as natural levees due to the coarse material deposited by the river.

5. Sand bars: These are the landforms formed inside the river at the mouth by deposition of large volume of sand, pebbles, alluvium and water.

6. Distributaries: Due to excessive load of water and silt at the mouth of river, the mainstream gets divided into several small channels of water known as distributaries.

7. Deltas: When soil  gets deposited between the distributaries in a triangular form, it is referred to as Delta. Deltas are very fertile lands found at the mouth of the river. For example, the Ganga-Brahmaputra delta is a very fertile delta found in West Bengal. 

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Question D.2:

How do sea waves modify the coastal regions?

Answer:

Sea waves are an important agent of erosion along with currents, storms and tides. But this erosion is mainly confined to sea coast only and results into several coastal landforms. Some of them can be understood with following points:

1. Sea caves: Due to the action of strong waves, the rock surface gets disintegrated and develops cavities. With time and continuos action of these sea waves, such cavities get enlarged and mould into cave-like structures referred to as sea caves.

2. Sea arch: When a single standing rock in the sea is faced with strong waves, its middle portion gets eroded. This forms a door  passage or an arch-like structure known as sea arch.

3. Stacks: As a result of the continuos action of sea waves over a long period of time, the roof of the sea arch also gets eroded leaving behind only the pillars known as stacks.

4. Sea cliff: When a sea wave strikes the surface of rock facing the sea for a long period, it erodes its roughness making it very sharp and steep towards the side of the sea. These landforms are referred as sea cliffs.

5. Beach: When the sea is calm, it deposits the silt, alluvium, sand and gravel that it brought with itself along the seashore. This results into the formation of long beaches

6. Lagoon: A partially enclosed lake formed when the sea water is trapped between the sea coast and sand bar is known as a lagoon. (Sand bars are the landforms formed inside the river at the mouth by deposition of a large volume of sand, pebbles, alluvium and water.)

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Question E.1:

Which of the following features is not formed by a river in the mountains?

a. gorge
b. canyon
c. meander
d. waterfall

Answer:

The correct answer is option (c).

Explanation: Except meanders, all the other three features are formed in the mountains. Meanders are formed by the rivers in plainsThey are the loops and curves that are formed by the rivers during their flow in the plains. 

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Question E.2:

A valley formed by a glacier resembles the letter

a. V
b. U
c. I
d. L

Answer:

The correct answer is option (b).

Explanation: A glacier forms a valley with steep sides and flat bottom by eroding rock minerals. This valley resembles the English alphabet 'U'  and hence, is known as the U-shaped Valley.

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Question E.3:

Loess is a type of

a. soil
b. rock
c. lake
d. sand dune

Answer:

The correct answer is option (a).

Explanation: Loess is a fine silted soil formed by the deposition of dust brought by the action of winds. It can be very fertile under favourable climatic conditions.

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Question E.4:

Which of the following lakes in India is a lagoon?

a. Wular
b. Sambhar
c. Govind Sagar
d. Chilka

Answer:

The correct answer is option (d).
 

Explanation: Chilka, a salt water lake of Orissa, is a very large lagoon. Wular, on the other hand, is a fresh water lake of Jammu & Kashmir, Sambhar is an inland salt lake of Rajasthan and Govind Sagar is a man-made reservoir in Himachal Pradesh.



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