Class 7 Geography Chapter 3 | Our Changing Earth | Expected Questions And Answers

Here are expected questions from chapter 3 of NCERT class 7 geography.

1. What are lithospheric plates?

The earth’s crust contains several large and some small irregularly shaped rigid slabs or plates. They hold the continents and the ocean floor. These are called lithospheric plates.

2. What are endogenic forces?

Endogenic forces are the forces within the interior of the earth that cause lithospheric plates to move.

3. What are exogenic forces?

Exogenic forces are the forces that work on the surface of the earth and cause lithospheric plates to move.

4. What causes volcanoes or earthquakes?

Endogenic forces that act within the interior of the earth sometimes cause sudden movements of the lithospheric plates. These sudden movements lead to earthquakes or volcanic eruptions that cause mass destruction on the surface of earth.

5. What are volcanoes?

A volcano is an opening in the earth’s crust through which molten materials erupt suddenly.

6. What causes earthquakes?

When the lithospheric plates move, the surface of the earth vibrates. These vibrations are called earthquakes. These vibrations travel all around the earth and cause considerable damage.

7. What is the focus of the earthquake?

The focus of the earthquake is the place in the crust where the movement of the lithospheric plate starts.

8. What is the epicentre of the earthquake?

The epicentre is the place on the surface of the earth just above the focus of the earthquake. Vibrations travel around the epicentre as waves. Areas near the epicentre suffer the greatest damage in the earthquake.

9. Name the instrument used to measure an earthquake

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Seismograph

10. Which scale is used to measure the magnitude of earthquake?

Richter Scale

11. How can earthquakes be predicted?

Earthquakes cannot be predicted; however, by studying animal behaviour we can get some clues. For example, immediately before an earthquake, snakes tend to come to the surface from their holes and fish in ponds get agitated.

12. Name the two processes that causes the landscape to wear away

Weathering and erosion

13. What is weathering?

Weathering is the breaking up of the rocks on the earth’s surface.

14. What is erosion?

Erosion is the wearing away of earth’s landscape by agents like water, wind and ice.

15. How are different landforms formed on the earth?

Wind, water and ice cause the wearing away of earth’s landscape. These agents also carry away the eroded material and eventually cause them to be deposited in various places. Over the course of time, this erosion and deposition form different landforms on earth.

16. How are waterfalls formed?

When water tumbles down hard rocks at a steep angle or when it flows down a steep valley, it forms a waterfall.

17. What is the highest waterfall in the world?

The Angel Falls of Venezuela

18. Name the waterfall on the border between Canada and USA

Niagara Falls

19. The Victoria Falls are located in the continent of ………………………

Africa

20. What are meanders?

Meanders are the large bends formed by a river as it flows over the plains.

21. How are floodplains formed?

When a river overflows its banks, it deposits a fine layer of fertile soil and other materials called sediments along its banks. This is how the flat fertile floodplains formed.

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22. What are levees?

The raised banks of a river are called levees.

23. What are distributaries?

Distributaries are the small streams that a river breaks up into as it approaches the sea.

24. What is delta?

As the river approaches the sea, it becomes very slow and begins to deposit the sediments it has bought. Each distributary has its own mouth where it deposits its load. The collection of deposits from all the mouths of a river forms a delta.

25. What are sea caves?

Sea caves are the hollow like waves formed on coastal rocks due to the constant striking of the sea waves.

26. Name some coastal landforms formed due to the erosion of sea waves?

Sea caves, sea arches and sea cliffs

27. How are beaches formed?

Beaches are formed when sea waves deposit sediments along the shores.

28. What are glacial moraines?

Glacial moraines are the materials such as rocks, sand and silt deposited by glaciers.

29. What is the main agent of erosion and deposition in the deserts?

Wind

30. What are mushroom rocks?

They are mushroom shaped rocks found in deserts.

31. What are sand dunes?

Sand dunes are the low-hill like structures found in the deserts where the sand gets deposited when the wind stops blowing.

32. What is loess?

Loess is a deposit of very thin and fine sand grains. Light sand grains get carried away by the wind over long distances. When such sand is deposited in large areas, it is called loess.

Choose the correct answer

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33. Which is not an erosional feature of sea waves? (cliff / beach / sea cave)

Beach

34. Which of the following is a depositional feature of a glacier? (flood plain / beach / moraine)

Moraine

35. Which of the following is caused by the sudden movements of the earth? (volcano / folding / flood plain)

Volcano

36. Mushroom rocks are found in: (deserts / river valleys / glaciers)

Deserts

37. Ox bow lakes are found in: (glaciers / river valleys / deserts)

River valleys

38. Which of the following is a depositional feature of sea waves? (floodplains / beaches / loess)

Beaches

Give reasons

39. Some rocks have the shape of a mushroom.

Mushroom rocks are found in deserts. Winds erode the lower section of the rocks more than the upper section. Consequently, rocks in deserts have narrower base and wider top. Since they resemble the shape of a mushroom, they are called mushroom rocks.

40. Floodplains are fertile

Rivers sometimes overflow their banks and then they deposit fine soil and other material along the banks. These sediments form flat floodplains that are highly fertile because of their rich alluvial deposits.

41. Sea caves are turned into stacks

When sea waves strike against coastal rocks, they form cave like structures on the rocks. These are called sea waves. Over time, these caves become bigger and bigger and then only the roof of the rock remains. These are called sea arches. Further erosion of the arches will break the roof and then only the walls of the cave will remain. These walls are called stacks.

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