Chapter 5 – Weathering

Weathering is an important chapter in WBBSE Class 9 Geography. Here, you will find Weathering questions and answers arranged clearly to help you revise quickly and prepare better for your exams.

Content Structure

1. Multiple choice questions and answers (MCQs)
2. Very short-type questions and answers
- 2A. Fill in the blanks
- 2B. True or false
- 2C. Single word questions and answers
3. Short-type questions and answers
4. Long-type questions and answers

1. Multiple choice questions and answers

1. The first stage of soil formation is-
(a) Batholith
(b) Solum
(c) Monolith
(d) Regolith

Ans: (d) Regolith

2. Which of the following is visible in homogeneous rocks?
(a) Block disintegration
(b) Exfoliation
(c) Biological weathering
(d) Granular disintegration

Ans: (b) Exfoliation

3. Snowfall prone areas experience-
(a) Chemical weathering
(b) Mechanical weathering
(c) Mechanical and chemical weathering
(d) Biological weathering

Ans: (b) Mechanical weathering

4. Conical rock formed due to frost action-
(a) Bajada
(b) Erg
(c) Pediment
(d) Talus

Ans: (d) Talus

5. Terrace farming is prevalent in-
(a) Deserts
(b) Coastal areas
(c) Plain areas
(d) Hilly areas

Ans: (d) Hilly areas

6. Soil erosion in desert areas takes place-
(a) Due to rivers
(b) Due to air stream
(c) Due to human beings
(d) Due to glaciers

Ans: (b) Due to air stream

7. The process in which the rocks of the surface of the earth gets disintegrated-
(a) Denudation
(b) Mass movement
(c) Erosion
(d) Disintegration

Ans: (d) Disintegration

8. A major factors of mechanical weathering-
(a) Oxygen
(b) Heat
(c) Hardness of rocks
(d) Gravitational force

Ans: (b) Heat

9. The process of humus formation iis-
(a) Humification
(b) Alluviation
(c) Regolith
(d) Mineralisation

Ans: (a) Humification

10. Cold regions experience-
(a) Mechanical weathering
(b) Chemical weathering
(c) Biological weathering
(d) Bio-mechanical weathering

Ans: (a) Mechanical weathering

11. The kind of weathering that takes place in heterogeneous rocks-
(a) Disintegration
(b) Exfoliation
(c) Granular disintegration
(d) Boulder cleaving

Ans: (d) Boulder cleaving

12. When water freezes into ice, its volume-
(a) Decreases by 8%
(b) Increases by 10%
(c) Increases by 9%
(d) Decreases by 11%

Ans: (c) Increases by 9%

13. The kind of weathering causing inselberg landforms-
(a) Carbonation
(b) Oxidation
(c) Exfoliation
(d) Hydrolysis

Ans: (c) Exfoliation

2. Very short-type questions and answers

2A. Fill in the blanks

1. Rock disintegration takes place in ___________ type of weathering. (mechanical)
2. Decomposition occurs in ___________ weathering. (chemical)
3. Oxidation is a type of _______________ weathering. (chemical)
4. Exfoliation is commonly found in __________ areas. (desert)
5. Limestone is dissolved as a result of ________________. (carbonation)
6. In areas of snowfall, ______________ weathering largely occurs. (mechanical)
7. Carbon dioxide mixed with water creates ____________ acid. (carbonic)
8. In tropical regions, ____________ weathering is largely seen. (chemical)
9. In heterogeneous rocks, _____________ takes place. (granular disintegration)
10. The breaking of rocks without chemical change is called _________________ (mechanical weathering).
11. The process by which humus is formed is known as ______________ (humification).
12. Rainwater mixed with carbon dioxide helps in the ________________ (solution of limestone).

2B. True or false

1. Weathering is the breakdown of rocks at their place of origin. (True)
2. Frost action is a common process of weathering in cold mountainous areas. (True)
3. Oxidation involves the reaction of iron minerals with oxygen. (True)
4. Regolith is the solid bedrock beneath the soil. (False)
5. Chemical weathering is dominant in desert regions. (False)
6. Talus is formed at the base of steep mountain slopes. (True)
7. Biological weathering is caused only by plants. (False)
8. Denudation includes weathering, erosion and mass wasting. (True)
9. Frost action occurs when water in rock cracks freezes and expands. (True)
10. Mechanical weathering is slowest in regions with extreme temperature variation. (False)

2C. Very short-type questions and answers

1. Decomposition of organic matter creates which acid?
Ans: Decomposition of organic matter creates humic acid.

2. Where does mass wasting occur?
Ans: Mass wasting occurs mainly on steep mountain slopes.

3. Give example of an easily soluble rock.
Ans: Limestone is an example of an easily soluble rock.

4. Mechanical weathering is predominant in which climatic regions?
Ans; Mechanical weathering is predominant in arid and semi-arid climatic regions.

5. Which type of weathering is prevalent in homogeneous rocks?
Ans: Mechanical weathering is prevalent in homogeneous rocks.

6. Which type of weathering occurs in limestone areas?
Ans: Chemical weathering occurs mainly in limestone areas.

7. What type of weathering is predominant in deserts?
Ans: Mechanical weathering is predominant in deserts.

8. Mechanical weathering takes place in which climate?
Ans: Mechanical weathering takes place in hot and dry climates.

9. Chemical weathering is active in which cliate?
Ans: Chemical weathering is active in hot and humid climates.

10. What type of weathering is active in temperature climate?
Ans: Mechanical weathering is active in the temperate climate.

11. What type of weathering is equatorial hot and humid climate?
Ans: Chemical weathering is dominant in the equatorial hot and humid climate.

12. What does granular disintegration take place?
Ans: Granular disintegration takes place due to alternate heating and cooling of rocks.

13. Which gaseous component is needed in oxidation?
Ans: Oxygen is the gaseous component needed in oxidation.

14. Combining of rock minerals with water is called?
Ans: The combining of rock minerals with water is called hydration.

15. Which type of weathering results in rusting of rocks?
Ans: Chemical weathering results in rusting of rocks.

16. Name a burrowing animal.
Ans: Earthworm is an example of a burrowing animal.

17. Exfoliation occurs in which type of rock?
Ans: Exfoliation occurs mainly in igneous rocks.

18. Ice distinegration occurs in which climatic region?
Ans: Ice disintegration occurs in cold and mountainous regions.

19. Which type of weathering causes changes in the structural composition of rocks?
Ans: Chemical weathering causes changes in the structural composition of rocks.

20. Which type of weathering is hydrolysis?
Ans: Chemical weathering involves the process of hydrolysis.

21. Which type of weathering is prevalent in the rainy tropical region?
Ans: Chemical weathering is prevalent in the rainy tropical region.

22. What type of chemical weathering is caused due to the reaction of iron with oxygen?
Ans: Oxidation is the chemical weathering caused due to the reaction of iron with oxygen.

23. Ferrous oxide is converted into which compound as result of oxidation?
Ans: Ferrous oxide is converted into ferric oxide as a result of oxidation.

24. Which process causes disintegration of rocks as a result of decrease in pressure of the rock layers?
Ans: Exfoliation causes disintegration of rocks due to decrease in pressure of rock layers.

25. The process whereby the rocks are broken apart is an example of which type of weathering?
Ans: The breaking apart of rocks is an example of mechanical weathering.

26. Who was the first to use the term ‘weathering’?
Ans: G. K. Gilbert was the first to use the term ‘weathering’.

27. Which type of weathering is predominant in the Thar Desert?
Ans: Mechanical weathering is predominant in the Thar Desert.

28. In which type of weathering does gunshot like noises occur?
Ans: Gunshot-like noises occur in exfoliation.

29. When weathering occurs as a natural process what is it called?
Ans: When weathering occurs naturally, it is called natural weathering.

30. What is the process by which the depth of gullies increases due to erosion called?
Ans: The increase in depth of gullies due to erosion is called vertical erosion.

31. What is the process of conserving soil by covering it with a layer of organic material called?
Ans: Conserving soil by covering it with organic material is called mulching.

3. Short-type questions and answers

1. What is mechanical weathering?
Ans: Mechanical weathering is the process by which rocks break into smaller pieces without any change in their chemical composition, mainly due to physical forces like temperature changes, frost action and pressure release.

2. Distinguish between weathering and erosion.
Ans:

Weathering	Erosion
Weathering is the breaking down of rocks in their original place in situ.	Erosion is the removal and transportation of weathered materials from one place to another.
It does not involve movement of rock materials.	It always involves movement of materials.
It is a slow and continuous process.	It may be slow or rapid depending on the agents.
It is caused by physical, chemical and biological processes.	It is caused by agents like water, wind, ice and waves.
Weathering is the first stage of denudation.	Erosion is the second stage of denudation.

3. What are the causes of mechanical weathering?
Ans: Mechanical weathering is caused by the following factors:

Temperature variation – Repeated heating and cooling cause rocks to expand and contract, leading to cracking.
Frost action – Water freezes in rock cracks, expands and breaks the rocks.
Pressure release – Removal of overlying rock layers causes the exposed rocks to peel off.
Wind action – Strong winds carrying sand particles wear away rock surfaces.
Running water – Flowing water strikes rocks repeatedly and breaks them into smaller pieces.

4. What is the relation between weathering and climate?
Ans:

Climate	Type of Weathering	Explanation
Hot and dry climate	Mechanical weathering	Large day–night temperature variation causes expansion and contraction of rocks.
Cold climate	Mechanical weathering	Frost action breaks rocks due to freezing and thawing of water.
Hot and humid climate	Chemical weathering	High temperature and moisture increase chemical reactions in rocks.
Tropical rainy climate	Chemical weathering	Heavy rainfall and heat accelerate processes like carbonation and oxidation.

5. How is rock disintegrated by plants and animals?
Ans: Plant roots grow into cracks and widen them, while animals burrow into the soil, both of which break rocks mechanically.

6. What is the role of human beings in biological weathering?
Ans: Human beings accelerate biological weathering through activities like mining, quarrying, construction of roads and buildings. These activities weaken rocks and increase their breakdown.

7. What is desert varnish?
Ans: Desert varnish is a dark, shiny coating formed on exposed rock surfaces in deserts due to oxidation of minerals like iron and manganese.

8. What are tors?
Ans: Tors are isolated and massive rock outcrops formed mainly due to long-term mechanical weathering, especially exfoliation.

9. Why is weathering also known as disintegration process?
Ans: Weathering is called disintegration because it breaks rocks into smaller pieces.

10. What is talus?
Ans: Talus is a cone-shaped accumulation of rock fragments at the base of a hill slope.

11. Why is carbonation more predominant in limestone regions?
Ans: Carbonation is more predominant in limestone regions because limestone reacts easily with carbonic acid, leading to its dissolution.

12. What is Terra Rossa?
Ans: Terra Rossa is a red residual soil formed from the weathering of limestone.

13. What is eluviation and illuviation?
Ans: Eluviation is the washing down of minerals from the upper soil layers, while illuviation is the accumulation of these minerals in the lower layers.

14. What is chemical weathering?
Ans: Chemical weathering is the process by which rocks are decomposed or altered chemically due to reactions with water, oxygen, carbon dioxide and acids.

15. What is erosion?
Ans: Erosion is the process by which weathered rock and soil materials are removed and transported from one place to another by agents like rivers, wind, glaciers and sea waves.

16. What are the different types of biological weathering?
Ans: Biological weathering takes place due to the activities of plants, animals and human beings, all of which help in breaking rocks.

17. What is block disintegration?
Ans: Block disintegration is the breaking of rocks into large angular blocks due to physical stress and pressure.

18. Where is terrace farming practiced?
Ans: Terrace farming is practiced on mountain slopes.

19. What is colloid plucking?
Ans: Colloid plucking is the process by which fine clay particles are removed by percolating water from the upper soil layers.

20. What is regolith?
Ans: Regolith is the loose, weathered layer of rock material that lies above the solid bedrock.

21. What is solum?
Ans: Solum is the upper soil layer where soil formation processes are active.

22. How does terrace farming help in conserving soil?
Ans: Terrace farming reduces the speed of runoff water, thereby preventing soil erosion.

23. Which type of landforms result from mechanical weathering?
Ans: Mechanical weathering forms landforms such as tors, talus and block mountains.

24. What are the controlling factors of weathering?
Ans: Climate, rock type, relief, vegetation and time are the main controlling factors of weathering.

25. How does weathering help in increasing soil fertility?
Ans: Weathering releases minerals and nutrients into the soil, which improve soil fertility.

4. Long-type questions and answers

1. How do the different processes of chemical weathering take place?
Ans: Chemical weathering is the process by which rocks are decomposed due to chemical reactions. It mainly takes place through the following processes:

Oxidation: Oxygen reacts with iron present in rocks to form rust (ferric oxide), weakening the rock.
Carbonation: Carbon dioxide dissolved in rainwater forms carbonic acid, which dissolves rocks like limestone.
Hydration: Minerals combine with water and expand, causing rocks to crack.
Hydrolysis: Water reacts with minerals and forms new softer minerals like clay.
Solution: Some minerals dissolve completely in water.

2. Why is mechanical weathering predominant in hot deserts?
Ans: Mechanical weathering is predominant in hot deserts mainly due to climatic conditions. Hot deserts experience extreme variation between day and night temperatures. During the day, intense heat causes rocks to expand, while at night, rapid cooling causes them to contract. This repeated expansion and contraction creates stress within the rocks, leading to cracks and finally breaking them into fragments. This process is known as insolation weathering or granular disintegration. Deserts receive very little rainfall, so chemical weathering is weak due to lack of moisture. Sparse vegetation also means there is little biological weathering. So, physical processes dominate. Therefore, due to high temperature variation, dryness and lack of vegetation, mechanical weathering is most active in hot desert regions.

3. Distinguish between weathering and erosion.
Ans:

Weathering	Erosion
Weathering is the breaking down of rocks in situ.	Erosion is the removal and transportation of weathered materials.
It occurs at the same place.	Materials are carried from one place to another.
Weathering does not require external agents.	Erosion requires agents like water, wind, ice and waves.
It is the first stage of denudation.	It is the second stage of denudation.

4. Distinguish between exfoliation and granular disintegration.
Ans:

Exfoliation	Granular Disintegration
Exfoliation occurs due to pressure release in rocks.	Granular disintegration occurs due to repeated temperature variation.
Outer layers peel off in curved sheets.	Rocks break into small grain-like particles.
It forms curved rock surfaces.	It forms sand-like particles.
It is common in massive rocks.	It is common in desert regions.

5. Distinguish between weathering and denudation.
Ans:

Weathering	Denudation
Weathering is the breaking of rocks at their place of origin.	Denudation is the wearing down of land by several processes.
It is an in situ process.	It includes movement of materials.
Weathering is a single process.	Denudation is a combination of processes.
It is the initial stage of landform development.	It is the overall process of lowering the land surface.

6. Distinguish between erosion and mass wasting.
Ans:

Erosion	Mass Wasting
Erosion is caused by external agents like water, wind and ice.	Mass wasting is caused mainly by gravity.
It involves horizontal movement of materials.	It involves vertical or downslope movement.
Erosion is generally slow and continuous.	Mass wasting may be sudden and rapid.
External agents are essential for erosion.	No transporting agents are required in mass wasting.

7. Distinguish between mechanical weathering and chemical weathering.
Ans:

Mechanical Weathering	Chemical Weathering
Mechanical weathering involves physical breakdown of rocks.	Chemical weathering involves chemical decomposition of rocks.
It does not change the chemical composition of rocks.	It changes the chemical composition of rocks.
It is dominant in dry and cold regions.	It is dominant in hot and humid regions.
It produces rock fragments.	It produces new minerals.

8. Difference between chemical weathering and biological weathering.
Ans:

Chemical Weathering	Biological Weathering
Chemical weathering is caused by chemical reactions in rocks.	Biological weathering is caused by living organisms.
Water and gases play an important role in this process.	Plants, animals and human activities are involved.
It alters the chemical composition of rocks.	It mainly causes physical changes in rocks.
It is controlled mainly by climate.	It is controlled by living organisms.