Our Environment

Book: Our Environment

Chapter: 3. Our Changing Earth

Subject: Social Science - Class 7th

Q. No. 1 of Exercise

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1

What are sand dunes?

As wind blows it carries sand other dust particles along it. As the speed of the wind slows down the sand and dust particles settle on the surface of the earth and forms pile. This phenomenon is responsible for the formation of sand dunes. Sand dunes are formed mostly in desert areas where sand is found is found in abundance. When wind blows in these areas, it lifts and transports sand from one place to another. When the wind stops blowing or reduces its speed, the heavier sand particles fall and get deposited in low hill-like structures. These are called the sand dunes.


3

More Exercise Questions

1

Why do the plates move?
1

What are exogenic and endogenic forces?
1

What is erosion?
1

How are flood plains formed?
1

What are sand dunes?
1

How are beaches formed?
1

What are ox-bow lakes?
2

Tick the correct Answer.

Which is not an erosional feature of sea waves?


(a) Cliff


(b) Beach


(c) Sea cave
2

Tick the correct Answer.

The depositional feature of a glacier is:


(a) Flood plain


(b) Beach


(c) Moraine
2

Tick the correct Answer.

Which is caused by the sudden movements of the earth?


(a) Volcano


(b) Folding


(c) Flood plain
2

Tick the correct Answer.

Mushroom rocks are found in:


(a) Deserts


(b) River valleys


(c) Glaciers
2

Tick the correct Answer.

Ox bow lakes are found in:


(a) Glaciers


(b) River valleys


(c) Deserts
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
4

Give reasons

Some rocks have a shape of a mushroom.
4

Give reasons

Flood plains are very fertile.
4

Give reasons

Sea caves are turned into stacks.
4

Give reasons

Buildings collapse due to earthquake Give reasons.
5

Activity.

Observe the photographs given below. These are various features made by a river. Identify them and also tell whether they are erosional or depositional or landforms formed by both.
6

For fun.

Solve the crossword puzzle with the help of given clues.



Across


2. Loop like bend of river


4. Solid form of water


7. Moving mass of ice


9. Sudden descent of water in bed of river


11. Natural cavity on weak rocks formed by action of waves


12. Embankment on river that keeps river in its channel


13. Large body of sea water


14. Dry area where sand dunes are found


15. Small hill of sand piled by action of wind


16. Flat plain formed by river deposits during time of flood


Down


1. Rise and fall of water caused by friction of wind on water surface


3. Flow of water in channel


5. Steep perpendicular face of rock along sea coast


6. Debris of boulder and coarse material carried by glacier


8. Crescent shaped lake formed by river meander


10. Fine sand deposited by action of wind


13. Isolated mass of rising steep rock near coastline


14. Alluvial tracts of land at mouth of river formed by river deposits