NCERT Solutions for Class 7 Social Science Geography Chapter 3 Our Changing Earth are part of NCERT Solutions for Class 7 Social Science. Here we have given NCERT Solutions for Class 7 Social Science Geography Chapter 3 Our Changing Earth.
|Subject||Social Science Geography|
|Chapter Name||Our Changing Earth|
|Number of Questions Solved||8|
NCERT Solutions for Class 7 Social Science Geography Chapter 3 Our Changing Earth
NCERT TEXTBOOK EXERCISES
Answer the following questions.
(i) Why do the plates move?
(ii) What are exogenic and endogenic forces?
(iii) What is erosion?
(iv) How are flood plains formed?
(v) What are sand dunes?
(vi) How are beaches formed?
(vii) What are ox-bow lakes?
(i) The plates move because of the movement of the molten magma inside the earth.
(ii) Exogenic forces. The forces that work on the surface of the earth are called exogenic forces.
Endogenic forces. The forces that act in the interior of the earth are called endogenic forces.
(iii) Erosion is the wearing away of the landscape by different agents like water, wind, and ice.
(iv) During floods, layers of fine soil and other material called sediments are deposited on the river bank. This leads to the formation of flat fertile flood plains.
(v) Sand dunes are low hill-like structures formed by the deposition of sand in the deserts.
(vi) Beaches are formed when the sea waves deposit sediments along the shores of the sea.
(vii) When the meander loop is cut off from the main river, it forms a cut-off lake. As its shape is like an oxbow, it is also known as an ox-bow lake.
Tick the correct answer.
(i) Which is not an erosional feature of sea waves?
(c) Sea cave
(ii) The depositional feature of a glacier is:
(a) Flood plain
(iii) Which is caused by the sudden movements of the earth?
(c) Flood plain
(iv) Mushroom rocks are found in:
(b) River valleys
(v) Ox-bow lakes are found in:
(b) River valleys
(b) River valleys.
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
(i) Glacier (c) River of ice
(ii) Meanders (d) Rivers
(iii) Beach (a) Seashore
(iv) Sand dunes (h) Deserts
(vi) Waterfall (g) Hard bedrock
(vi) Earthquake (e) Vibrations of earth.
(i) Some rocks have a shape of a mushroom.
(ii) Flood plains are very fertile.
(iii) Sea caves are turned into stacks.
(iv) Buildings collapse due to earthquakes.
(i) In deserts, winds usually erode the lower section of the rock more than the upper part. Therefore, such rocks have a narrower bases and wider tops, which take the shape of a mushroom.
(ii) Flood plains are formed by the deposition of fine soil and other material called sediments on the river banks. As the soil and sediments are brought by floodwater, they are very fertile.
(iii) Sea waves strike at the rocks. As a result, cracks develop which become bigger over time and hollow like caves are formed on the rocks. They are called sea caves. These cavities become bigger and bigger and a time comes when only the roof of the caves remains to form sea arches. Further erosion breaks the roof and only walls are left. These wall-like features are called stacks. In this way, sea caves are turned into stacks.
(iv) 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.
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.
|Photograph||Nature of the Feature||Type (Erosional or depositional or Both|
Solve the crossword puzzle with the help of given clues.
2. Loop like the bend of a river.
4. Solid form of water.
7. Moving mass of ice.
9. Sudden descent of water in the bed of a river.
11. Natural cavity on weak rocks formed by the action of waves.
12. Embankment on a river that keeps it in its channel.
13. Large body of seawater.
14. Dry area where sand dunes are found.
15. Small hill of sand caused by the action of the wind.
16. Flat plain formed by river deposits during the time of the flood.
1. Rise and fall of water caused by friction of the wind on the water surface.
3. Flow of water in a channel.
5. Steep perpendicular face of rock along a sea coast.
6. Debris of boulder and coarse material carried by a glacier.
8. Crescent-shaped lake formed by a meandering river.
10. Fine sand deposited by the action of the wind.
13. Isolated mass of rising steep rock near a coastline.
14. Alluvial tracts of land formed by the river deposits at the mouth of a river.
Earthquake-A case study
1. Read the ‘Earthquake – A case study’ given in the form of headlines that appeared in the newspapers after the quake. Arrange the events in the right sequence of their happening.
2. Imagine if a quake suddenly shook in the middle of the school day, where do you go for safety?
2. We would go for safety
- in the open
- under the gates
- would keep pillow or cushion on our heads.
INTEXT QUESTIONS WITH THEIR ANSWERS
Find out the names of a few rivers of the world that form a delta?
Name of some rivers (See the Map):
- The Nile.
- Hwang Ho.
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