NCERT Solutions for Chapter 3 Our Changing Earth Class 7 Geography
Book Solutions1(i)
Answer the following questions.
(i) Why do the plates move?
Answer
The plates move because of the movement of the molten magma inside the earth.
Exercises
Page Number 17
1(ii)
Answer the following questions.
What are exogenic and endogenic forces?Answer
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 as endogenic forces.
The forces which act in the interior of the earth are called as endogenic forces.
Exercises
Page Number 17
1(iii)
Answer the following questions.
What is erosion?
What is erosion?
Answer
The wearing away of the landscape by different agents like water, wind and ice is called erosion.
Exercises
Page Number 17
1(iv)
Answer the following questions.
How are flood plains formed?
How are flood plains formed?
Answer
When river overflows its banks, it flood off its neighbouring areas which deposits layers of fine soil and other
material called sediments along its banks. This leads to the formation of a flat fertile floodplain.
Exercises
Page Number 17
1(v)
Answer the following questions.
What are sand dunes?
What are sand dunes?
Answer
The low hill like structures formed due to deposition of sand at one place by the wind in the desert is called sand dunes.
Exercises
Page Number 17
1(vi)
Answer the following questions.
How are beaches formed?
How are beaches formed?
Answer
The sea waves deposit sediments along the shores which leads to the formation of beaches.
Exercises
Page Number 17
1(vii)
Answer the following questions.
What are ox bow lakes?
What are ox bow lakes?
Answer
Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loop come closer and closer which in some time cuts off from the river and forms a cut-off lake, called an ox-bow
lake.
Exercises
Page Number 17
2(i)
Tick the correct answer.
(i) Which is not an erosional feature of sea waves?
(a) Cliff
(b) Beach
(c) Sea cave
(a) Cliff
(b) Beach
(c) Sea cave
Answer
✓ (b) Beach
Exercises
Page Number 17
2(ii)
Tick the correct answer.
The depositional feature of a glacier is:(a) Flood plain
(b) Beach
(c) Moraine
Answer
✓ (c) Moraine
Exercises
Page Number 17
2(iii)
Tick the correct answer.
Which is caused by the sudden movements of the earth?(a) Volcano
(b) Folding
(c) Flood plain
Answer
✓ (a) Volcano
Exercises
Page Number 17
2(iv)
Tick the correct answer.
Mushroom rocks are found in:(a) Deserts
(b) River valleys
(c) Glaciers
Answer
✓ (a) Deserts
Exercises
Page Number 17
2(v)
Tick the correct answer.
Ox bow lakes are found in:(a) Glaciers
(b) River valleys
(c) Deserts
Answer
✓ (b) River valleys
Exercises
Page Number 17
3
Match the following.
(i) Glacier | (a) Sea shore |
(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) Sea cliff |
- | (g) Hard bed rock |
- | (h) Deserts |
Answer
(i) Glacier | (c) River of ice |
(ii) Meanders | (d) Rivers |
(iii) Beach | (a) Sea shore |
(iv) Sand dunes | (h) Deserts |
(v) Waterfall | (f) Sea cliff |
(vi) Earthquake | (e) Vibrations of earth |
Exercises
Page Number 18
4(i)
Give reasons.
Some rocks have a shape of a mushroom.
Answer
In desert, wind is an active agent for erosion which erode the lower section of the rock more than the upper part. Therefore, some rocks have a shape of a mushroom having narrower base and wider top.
Exercises
Page Number 18
4(ii)
Give reasons.
Flood plains are very fertile.
Answer
Flood plains are very fertile because floods deposit layers of fine soil and other material called sediments which is ideal for cultivation along its banks.
Exercises
Page Number 18
4(iii)
Give reasons.
Sea caves are turned into stacks.
Answer
When cavities in sea caves become bigger and bigger only the roof of the caves remain forming sea arches. Further, erosion breaks the roof and only walls are left which forms the stacks.
Exercises
Page Number 18
4(iv)
Give reasons.
Buildings collapse due to earthquakes. Answer
During earthquakes, vibrations travel outwards from the epicentre as waves and propagate through the surface of the earth which produce sudden movements that leads to the collapse of buildings.
Exercises
Page Number 18