Class 9 Social Geography Chapter 1 Changes of the Earth’s Surface
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Part II: Geography
Changes of the Earth’s Surface
Lesson-Based Questions &Answers
Short Answer Type Questions
1. Give an overview of the distribution of continents and oceans on the Earth’s surface.
Ans: The Earth’s surface is composed of continents and oceans. About 71percent is COVERED by water and 29 percent by land.
The land includes plains, mountains, rivers, valleys, deserts, coastal plains, etc.
On the other hand, the oceans are filled with water, and beneath them there are plateaus, plains, deep trenches, mountain ranges, and islands of different sizes.
2. Explain why changes occur on the Earth’s surface.
Ans: Changes on the Earth’s surface occur due to some external and internal factors.
External factors include wind, rain, heat of the sun, rivers, sea waves, glaciers, etc.
Internal factors include earthquakes and volcanic eruptions.
3. What are external factors? Name some external factors.
Ans: The factors that cause changes on the Earth’s surface from outside are called external factors.
Some external factors are wind, rain, heat of the sun, rivers, sea waves, glaciers, etc.
4. Why are earthquakes and volcanoes called internal factors?
Ans: Earthquakes and volcanoes originate from within the Earth’s surface, so they are called internal factors. These factors bring changes not only on the surface but also in the interior of the Earth.
5. What is meant by a river basin? Draw a diagram of a river basin.
Ans: A river carries rainwater, water stored on mountains, melted snow, etc. through its tributaries and distributaries. The area through which a river and its tributaries flow is called a river basin.
6. What is a tributary? Name two major tributaries of the Brahmaputra.
Ans: A tributary is a river that flows from its source through plains and joins a larger river. Two tributaries of the Brahmaputra are Manas and Dhansiri.
7. Give an idea about river erosion.
Ans: The wearing away of riverbanks by the flow of a river is called river erosion. When a river carries more water, its speed increases and exerts pressure on both banks, causing erosion. This process is more intense during the rainy season. Erosion carries rocks, sand, and soil from higher regions and deposits them in lower regions.
8. What is lateral erosion of a river?
Ans: As a river flows from highland to plains, its speed changes. In plains, due to reduced depth, it exerts pressure on both sides, causing the banks to collapse. This process is called lateral erosion.
9. What is an ox-bow lake? Explain its formation with figure.
Ans: When a river flows through plains, it follows a winding or meandering course. In some places, the bends become very sharp. During floods, the river cuts across the bends and follows a straighter path, leaving behind thecurved section. This abandoned section, shaped like a horseshoe, later fills with water and forms an ox-bow lake.
10. What is a floodplain and how is it formed?
Ans: During floods, rivers deposit silt and mud on both sides of their banks, forming floodplains. These plains are fertile and suitable for agriculture.
11. How are sandbars formed in a river?
Ans: Sand and silt carried by rivers get deposited either along the banks orin the middle of the river, forming sandbars. These are temporary and vary in shape.
12. How is a delta formed?
Ans: A delta is formed when sediments carried by a river are deposited at its mouth in a shallow sea. These deposits form land shaped like the Greek letter delta, hence called a delta.
13. Why is the action of wind strong in deserts?
Ans: In deserts, there is little or no vegetation, so wind can act more freely and strongly.
14. What is deflation?
Ans: In deserts, strong winds carry sand from one place and deposit it elsewhere. This process of removal and transportation of sand by wind is called deflation.
15. How are sand dunes formed?
Ans: Sand carried by wind gets deposited in one place and gradually accumulates into heaps, forming sand dunes.
16. What is an Inselberg?
Ans: An Inselberg is an isolated hill found in deserts formed due to erosion. The term means a solitary hill rising like an island.
17. Define a glacier and state its difference from a river.
Ans: A glacier is a mass of accumulated ice in very cold regions that moves slowly down slopes.
Differences:
(a) Rivers flow rapidly, whereas glaciers move slowly.
(b) Rivers consist of flowing water, whereas glaciers are masses of ice.
(c) Rivers are found in warm regions, while glaciers are found in cold regions.
18. What is ‘grab’ (glacial debris)? Name its types.
Ans: Materials carried by glaciers such as rocks and soil are collectively called glacial debris (moraine). Types include lateral, ground, medial, and terminal moraines.
19. How are sharp peaks formed by glaciers?
Ans: Glaciers carry rocks and debris and erode the land through friction. Continuous erosion from all sides makes mountain tops sharp and pointed.
20. What is a coast?
Ans: The boundary or shore of seas and oceans is called a coast.
21. What is a beach? State its importance.
Ans: Continuous action of waves makes coastal areas uneven. When large amounts of sand accumulate along the shore, a gently sloping landform called a beach is formed. Beaches are important for recreation and tourism.
22. How do sea waves change coastal areas?
Ans: Waves, along with rain and wind, continuously act on coastal areas and bring changes in landforms, depth, vegetation, and geological structure.
23. Match the factors with landforms.
Ans: River – Floodplain
Wind – Sand dunes
Glacier – U-shaped valley
Sea waves – Coast
24. What kind of changes may occur on the Earth’s surface in the future?
Ans: Changes on the Earth’s surface are continuous due to internal and external factors. In the future, human activities will also influence these changes. Increased carbon dioxide may raise temperature, melt polar ice, and raise sea levels, submerging many regions. Strong winds, cyclones, desertification, shifting river courses, and reduced agricultural production may occur, making Earth less suitable for habitation.
25. Write a note on the physical features of your village or town. Drawa diagram showing major landforms.
Ans: Try yourself.
Additional Questions and Answers
1. What is an earthquake?
Ans: The vibration of the Earth caused by internal factors such as volcanic eruptions or the sinking of large land masses due to excavation or other causes is called an earthquake.
2. What is the name of the ‘delta’ located in the Brahmaputra River?
Ans: Majuli.
3. What is meant by a coastline?
Ans: The boundary between continents and oceans appears as an irregular, long line. This line is called a coastline.
4. What is a yardang?
Ans: A yardang is a type of landform consisting of long ridges and shallow elongated depressions formed by wind erosion on soft rocks.
5. What is a sea cliff?
Ans: When the coastal part of the sea consists of hard rocks like granite or basalt, sea waves erode them and form steep cliffs. Such steep cliffs are called sea cliffs.
6. What is a tsunami?
Ans: When a strong earthquake occurs under the sea, special types of waves are generated in oceans. These waves gain abnormal height and nearthe coast and cause massive destruction. Such destructive waves are called tsunamis.
7. In which year did the devastating tsunami in Japan occur?
Ans: In 2011.
Multiple Choice Questions (MCQs)
1. What percentage of the Earth’s surface is covered by water?
(a) 29%
(b) 50%
(c) 71%
(d) 90%
Ans: (c)
2. Which of the following is an external factor of surface change?
(a) Earthquake
(b) Volcano
(c) Wind
(d) Tectonic movement
Ans: (c)
3. Which of the following is an internal factor?
(a) Rain
(b) Glacier
(c) Earthquake
(d) River
Ans: (c)
4. What is a river basin?
(a) The mouth of a river
(b) The area drained by a river
(c) The source of a river
(d) A river island
Ans: (b)
5. Which of the following is a tributary of the Brahmaputra?(a) Ganga
(b) Yamuna
(c) Manas
(d) Nile
Ans: (c)
6. What is river erosion?
(a) Deposition of soil
(b) Breaking of river banks
(c) Formation of delta
(d) Drying of river
Ans: (b)
7. Lateral erosion mainly occurs in which region?
(a) Mountain
(b) Plateau
(c) Plain
(d) Desert
Ans: (c)
8. What is an ox-bow lake?
(a) A deep sea lake
(b) A straight river path
(c) A horseshoe-shaped lake
(d) A glacier lake
Ans: (c)
9. Floodplains are formed by:
(a) Wind
(b) River deposition
(c) Volcano
(d) Earthquake
Ans: (b)
10. Sandbars are formed due to:
(a) Earthquake
(b) River deposition
(c) Glacier melting
(d) Rainfall
Ans: (b)
11. What is the shape of a delta?
(a) Circular
(b) Square
(c) Triangular
(d) Rectangular
Ans: (c)
12. Wind action is strongest in:
(a) Forest
(b) Desert
(c) Mountain
(d) Plateau
Ans: (b)
13. What is deflation?
(a) Deposition by water
(b) Removal of sand by wind
(c) Formation of glacier
(d) River erosion
Ans: (b)
14. Sand dunes are formed by:
(a) Rivers
(b) Glaciers
(c) Wind
(d) Volcano
Ans: (c)
15. What is an Inselberg?
(a) A river valley
(b) A desert hill
(c) A glacier
(d) A delta
Ans: (b)
16. Glaciers move:
(a) Very fast
(b) Moderately
(c) Slowly
(d) Not at all
Ans: (c)
17. What is moraine?
(a) River deposit
(b) Wind deposit
(c) Glacier deposit
(d) Sea deposit
Ans: (c)
18. Sharp peaks are formed due to:
(a) Wind
(b) River
(c) Glacier erosion
(d) Rain
Ans: (c)
19. What is a coast?
(a) Mountain edge
(b) River bank
(c) Land near sea
(d) Desert area
Ans: (c)
20. Beaches are formed by:
(a) Wind
(b) Glacier
(c) Sea waves
(d) Earthquake
Ans: (c)
21. Which factor continuously changes coastal areas?
(a) River
(b) Wind
(c) Sea waves
(d) Glacier
Ans: (c)
22. What is a coastline?
(a) Straight line
(b) Circular line
(c) Irregular boundary between land and sea
(d) Mountain line
Ans: (c)
23. What is a yardang?
(a) River valley
(b) Wind-eroded landform
(c) Glacier
(d) Delta
Ans: (b)
24. Sea cliffs are formed by:
(a) Wind
(b) Glacier
(c) Sea waves
(d) River
Ans: (c)
25. Tsunami is caused by:
(a) Rain
(b) Wind
(c) Undersea earthquake
(d) Glacier
Ans: (c)
26. Majuli is an example of:
(a) Desert
(b) Delta island
(c) Mountain
(d) Plateau
Ans: (b)
27. Floodplains are suitable for:
(a) Mining
(b) Industry
(c) Agriculture
(d) Fishing
Ans: (c)
28. Glaciers are found in:
(a) Hot regions
(b) Desert
(c) Cold regions
(d) Coastal areas
Ans: (c)
29. Which process forms U-shaped valleys?
(a) River erosion
(b) Wind action
(c) Glacier action
(d) Rainfall
Ans: (c)
30. Increase in carbon dioxide may cause:
(a) Cooling
(b) No change
(c) Global warming
(d) Earthquake
Ans: (c)
31. Which process is responsible for the formation of ox-bow lakes?(a) Vertical erosion
(b) Lateral erosion and cut-off
(c) Wind deposition
(d) Glacial erosion
Ans: (b)
32. Which landform is formed by river deposition at its mouth?(a) Inselberg
(b) Delta
(c) Moraine
(d) Yardang
Ans: (b)
33. Which type of moraine is formed in the middle of glaciers?(a) Lateral moraine
(b) Terminal moraine
(c) Medial moraine
(d) Ground moraine
Ans: (c)
34. Which factor mainly controls wind erosion in deserts?
(a) High rainfall
(b) Vegetation cover
(c) Lack of vegetation
(d) River flow
Ans: (c)
35. Which feature indicates strong glacial erosion?
(a) V-shaped valley
(b) U-shaped valley
(c) Sand dune
(d) Delta
Ans: (b)
36. What happens when polar ice melts due to global warming?
(a) Sea level falls
(b) Sea level rises
(c) No effect
(d) Rivers dry up
Ans: (b)
37. Which of the following is NOT formed by wind?
(a) Sand dune
(b) Yardang
(c) Delta
(d) Deflation hollow
Ans: (c)
38. Floodplains are mainly composed of:
(a) Rocks
(b) Lava
(c) Alluvial soil
(d) Ice
Ans: (c)
39. Which landform is created by wave erosion on hard rocks?
(a) Beach
(b) Delta
(c) Sea cliff
(d) Sandbar
Ans: (c)
40. Which factor contributes to long-term changes of Earth’s surface?
(a) Only internal factors
(b) Only external factors
(c) Both internal and external factors
(d) None
Ans: (c)
