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

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

Class 7 Geography Chapter 3 Our Changing Earth InText Questions and Answers

Text Book Page No. 14

Question 1.
Read the ‘Earthquake – A case study’ given in the form of headlines that appeared in the newspapers of the quake. Arrange the events in the right sequence of their happening.
Answer:

1. Earthquake hit Bhuj
2. Destruction of Bhuj
3. School worst affected
4. Fire in the city
5. CM’s appeal to the Centre
6. Bhuj relief effort blighted
7. Emergency declared in quake zone

Question 2.
Imagine if a quake suddenly shook in the middle of the school day, where would you go for safe.
Answer:
First of all, I would go to a safe place and hide myself under a table or desk.

Text Book Page No. 16

Question 1.
Can you find out names of some rivers of the world that form delta?
Answer:

1. Mississipi
2. Hwang Ho
3. Nile
4. Tigris
5. Euphrates
6. Indus

Class 7 Geography Chapter 3 Our Changing Earth Exercise Questions and Answers

Question 1.
Answer the following questions :

(1) Why do the plates move?
Answer:
The plates move because of the movement of the molten magma inside the earth.

(2) What are exogenic and endogenic forces?
Answer:
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.

(3) What is erosion?
Answer:
Erosion is the wearing away of the landscape by different agents like water, wind, and ice.

(4) How are flood plains formed?
Answer:
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.

(5) What are sand dunes?
Answer:
Sand dunes are low hill-like structures formed by the deposition of sand in the deserts.

(6) What are ox-bow lakes?
Answer:
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.

Question 2.
Tick the correct answer:

(1) Which is not an erosional feature of sea waves?
(a) Cliff
(6) Beach
(c) Sea cave
Answer:
(a) Cliff

(2) The depositional feature of a glacier is :
(a) Flood plain
(6) Beach
(c) Moraine
Answer:
(c) Moraine

(3) Which is caused by the sudden movement of the earth?
(a) Volcano
(6) Folding
(c) Flood plain
Answer:
(a) Volcano

(4) Mushroom rocks are found in :
(a) Deserts
(b) River valleys
(c) Glaciers
Answer:
(a) Deserts

(5) Oxbow lakes are found in :
(a) Glaciers
(b) River valleys
(c) Deserts
Answer:
(b) River valleys

Question 3.
Match the following:

Glacier	Sea-shore
Meanders	River of ice
Beach	Rivers
Sand dunes	Vibrations of earth
Waterfall	Hard bedrock
Earthquake	Deserts

Answer:

Glacier	River of ice
Meanders	Rivers
Beach	Sea-shore
Sand dunes	Deserts
Waterfall	Hard bedrock
Earthquake	Vibrations of earth

Question 4.
Give reasons.

(1) Some rocks have a shape of a mushroom.
Answer:
In deserts, winds usually erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower bases and wider tops, which take the shape of a mushroom.

(2) Flood plains are very fertile.
Answer:
Flood plains are formed when the river overflows its banks. It deposits layers of fine soil and other material called sediments which are very fertile.

(3) Sea caves are turned into stacks.
Answer:
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.

(4) Buildings collapse due to earth-quakes.
Answer:
Most of the buildings are not safe enough to resist the vibrations of earthquakes. They are not made earthquake-proof. They collapse tearing apart due to shallow foundation and lack of adequate steel in the interior design.

Activity

Question 5.
Observe the photographs given (in textbook page 18). These are various features made by a river. Identify them and also tell whether they are erosional or depositional or both landforms.
Answer:

Name of the Feature	Type (Erosional or Depositional or Both)
Waterfall Meander Flood plain	Erosional: Erosional and Depositional Depositional

FOR FUN

Question 6.
Solve the crossword puzzle with the help of given clues (see Textbook Page 19).
Answer: