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

Our Changing Earth

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

Exercise Questions and Answers

Question 1.
Answer the following questions :

(1) Why do the plates move?

Answer:
The plates move due to endogenic forces acting in the interior of the earth.

(2) What are exogenic and endogenic forces? ‘

Answer:
The forces that act in the interior of the earth are called endogenic forces. The forces that act on the earth’s surface are called exogenic 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:
When rivers outflow their banks, they cause floods in the neighbouring areas. The flood water takes away fine soil and other material and deposit them along the banks. This deposition leads to the formation of flood plains.

(5) What are sand dunes?

Answer:
Winds lift and carry sand from one place to another. When they stop blowing, sand falls and gets deposited in low hill-like structures called sand dunes.

(6) What are ox-bow lakes?

Answer:
When a river enters the plain, it forms a large bend which is cut-off from the main stream in due course of time. The cut off stream takes the form of a lake called oxbow 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) Ox bow lakes are found in :
(a) Glaciers
(b) River valleys
(c) Deserts
Answer:
(b) River valleys

Question 3.
Match the following :

GlacierSea-shore
MeandersRiver of ice
BeachRivers
Sand dunesVibrations of earth
WaterfallHard bed rock
EarthquakeDeserts

Answer:

GlacierRiver of ice
MeandersRivers
BeachSea-shore
Sand dunesDeserts
WaterfallHard bed rock
EarthquakeVibrations of earth

Question 4.
Give reasons.

(1) Some rocks have a shape of a mushroom.

Answer:
Because winds erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower base and wider top.

(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:
After the formation of sea caves when cavities become bigger only the roof of cave remain, sea arches are formed. Further, erosion breaks the roof and only walls are left. These wall like features are called stacks.

(4) Buildings collapse due to earth-quakes.

Answer:
In an earthquake the vibrations travel outwards from the epicentre as waves. The surface starts vibrating which lead to shaking of structures built on the earth’s surface and thus buildings collapse.

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 FeatureType (Erosional or Depositional or Both)
Waterfall Meander Flood plainErosional : Erosional and Depositional Depositional

FOR FUN

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

Answer:

NCERT SolutNCERT Solutions for Class 8 Social Science geography 3 img 1ions for Class 8 Social Science geography 3 img 1

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