NCERT Solutions for Class 7 Geography Chapter 3 Our Changing Earth

NCERT Solutions for Class 7 Geography Chapter 3 Our Changing Earth Social Science

In this page NCERT Solutions for Class 7 Geography Chapter 3 Our Changing Earth will help in building a strong foundation of concepts from the very beginning thus students will be given an easy and straightforward learning path. These NCERT Solutions for students help them with their research in analyzing problems and answering it with precision and the right concepts. You will experience the wonder and beauty in all that you are learning.

Chapter 3 Our Changing Earth NCERT Solutions for Class 7 Geography

1. Answer the following questions.

(i) Why do the plates move? 

Solution

The plates move because of the movement of the molten magma inside the earth.

(ii) What are exogenic and endogenic forces? 

Solution

The forces that work on the surface of the earth are called as exogenic forces. The forces which act in the interior of the earth are called endogenic forces.

(iii) What is erosion?

Solution

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

(iv) How are flood plains formed? 

Solution

During floods, layers of fine soil and other material called sediments are deposited on the river bank. This leads to the formation of a flat fertile flood plains.

 

(v) What are sand dunes? 

Solution

The low hill-like structures formed due to deposition of sand at one place by the wind in the desert is called sand dunes.

(vi) How are the beaches formed?

Solution

The sea waves deposit sediments along the shores which leads to the formation of beaches.

(vii) What are oxbow lakes?

Solution

When the meander loop is cut off from the main river, it forms a cut-off lake. As its shape is like an ox bow, it is also known as ox-bow lake.

2. Tick the correct answer. 

(i) Which is not an erosional feature of sea waves?

(a) Cliff 

(b) Beach

(c) Sea cave

Solution (b) Beach

(ii) The depositional feature of a glacier is:

(a) Flood plain 

(b) Beach 

(c) Moraine

Solution (c) Moraine

(iii) Which is caused by the sudden movements of the earth? 

(a) Volcano 

(b) Folding 

(c) Flood plain

Solution (a) Volcano

(iv) Mushroom rocks are found in: 

(a) Deserts 

(b) River valleys 

(c) Glaciers

Solution (a) Deserts

(v) Oxbow lakes are found in:

(a) Glaciers 

(b) River valleys 

(c) Deserts 

Solution (b) River valleys

3. Match the following.

(i) Glacier	(a) Seashore
(ii) Meanders	(b) Mushroom rock
(iii) Beach	(c) River of ice
(iv) Sand dunes	(d) Rivers
(v) Waterfall	(e) Vibrations of earth
(vi) Earthquake	(f) Seacliff
	(g) Hard bedrock
	(h) Deserts

Solution

(i) Glacier	(c) River of ice
(ii) Meanders	(d) Rivers
(iii) Beach	(a) Seashore
(iv) Sand dunes	(h) Deserts
(v) Waterfall	(f) Seacliff
(vi) Earthquake	(e) Vibrations of earth

4. Give reasons.

(i) Some rocks have the shape of a mushroom.

Solution

In deserts, the wind is a natural cause of erosion which erodes the lower section of rocks more than the upper portion. Therefore, some rocks have a distinctive shape of a mushroom with a narrow base and wider top.

(ii) Flood plains are very fertile.

Solution

Flood plains are very fertile because floods deposit layers of fine soil and other material called sediments which is ideal for cultivation.

(iii) Sea caves are turned into stacks.

Solution

When cavities in sea caves become bigger and bigger, the roof of the caves is all that remains. The remaining roof is eroded, breaking into a stack of walls.

(iv) Buildings collapse due to earthquakes.

Solution

Most of the buildings are not safe enough to resist the vibrations of the earthquakes. They are not made earthquake-proof. They collapse tearing apart due to shallow foundation and lack of adequate steel in the interior design.