Ch – 3 Our Changing Earth (Q-A)

Q.1: Answer the following questions:

a) Why do the plates move ?

Ans: The movement of molten magma inside the earth causes the plates to move.

b) What are exogenic and endogenic forces ?

Ans: The forces that act in the interior of the earth are called “Endogenic” forces. The forces that act on the surface of the earth are called “Exogenic” forces.

c) What is erosion ?

Ans: Erosion is the wearing away of the landscape by different agents like water, wind and ice.

d) How are flood plains formed ?

Ans: When the river overflows its banks, it floods the neighbouring areas. As it floods, it deposits layers of fine soil and other material called sediments along its banks. This leads to the formation of flood plains.

e) What are sand dunes ?

Ans: When the wind stops blowing the sand, it falls and gets deposited in a low hill-like structures called sand dunes.

f) How are beaches formed ?

Ans: The sea waves deposits sediments along the shores, which leads to the formation of beaches.

g) What are ox bow lakes ?

Ans: When the meander loop cuts off the river and forms a cut-off lake, it is known as an ox bow lake.

Q.2: Give reasons:

a) Some rocks have a shape of a mushroom.

Ans: Because winds erode the lower section of the rock more than the upper part.

b) Flood plains are very fertile.

Ans: Because it contains a deposit of fine soil and other materials called as sediments.

c) Sea caves are turned into stacks.

Ans: Because erosion breaks down the roof and then only walls are left.

d) Buildings collapse due to earthquakes.

Ans: Because the earth vibrates when an earthquake occurs.

Published by Priya Prakash

In the midst of winter, i found there was within me an invincible summer ~ Albert Camus

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