Weathering: ICSE Class 9 Geography solution

Summary

The Earth’s surface is always changing. Forces from inside the Earth build up land. Other forces work on the Earth’s surface from outside. These get energy from the sun, and climate affects how they work. One of these outside processes is weathering.

Weathering is how rocks break down or decay. It happens to rocks on or near the Earth’s surface when they are exposed to weather. Imagine a rock outside for a long time. Temperature changes, moisture, and rain slowly break it. Weathering is just the breaking down; the pieces are not carried away yet. This cannot happen on the Moon, as it lacks weather.

Weathering has key features. It breaks solid rocks into smaller pieces. It depends on the climate and rock type. A rock’s hardness, or how easily water enters it affects its weathering. Weathering changes the Earth’s surface and helps form soil. It turns large, hard rocks into finer materials.

There are three main types of weathering: physical, chemical, and biological.

Physical weathering breaks rocks into smaller pieces. It does not change what the rocks are made of. Temperature changes are a major cause. In hot deserts, rocks expand in heat and shrink in cold. This repeated action can cause block disintegration, splitting rocks into blocks. If rocks have different minerals, they may crumble into grains; this is granular disintegration. Frost action happens when water in cracks freezes and expands, pushing rocks apart. Exfoliation is when outer rock layers peel off, like an onion’s skin, due to sudden temperature changes.

Chemical weathering changes the materials in the rock. It decomposes rocks through chemical reactions. Water, oxygen, and carbon dioxide are common agents. Oxidation is like iron rusting. When iron in rocks meets oxygen, it crumbles and changes color. Carbonation occurs when rainwater with carbon dioxide forms a weak acid. This acid dissolves rocks like limestone. Hydration is when rock minerals absorb water and expand, breaking them down. Solution is when rock minerals dissolve in water.

Biological weathering is caused by living things. Humans cause it by mining or building roads. Plant roots can grow into rock cracks and split them. Yet, plants also protect rocks by holding soil. Animals’ and insects’ burrowing can loosen rock material. Decaying plants and animals can also release chemicals that weather rocks.

Weathering varies with climate. In hot, wet equatorial areas, chemical weathering is strong. In tropical areas with wet and dry seasons, special chemical reactions can form laterite soils. Deserts, with big daily temperature changes, have much physical weathering. In temperate regions, frost action is powerful. In cold polar regions, frost causes physical weathering. Melting ice there can also cause some chemical weathering.

Textbook solutions (Morning Star/Total)

Multiple-Choice Questions

1. The process of breaking down of rocks but not their removal:

(a) Weathering
(b) Block Disintegration
(c) Oxidation
(d) Mechanical Weathering

Answer: (a) Weathering

2. Which amongst the following is NOT a characteristic of Weathering?

(a) It affects the surface of the earth
(b) It changes hard massive rocks into finer materials
(c) It causes disintegration of soil
(d) It involves disintegration or decay of solid rocks

Answer: (c) It causes disintegration of soil

3. Rock disintegration without any change in the chemical constituents of the rock:

(a) Block Disintegration
(b) Mechanical Weathering
(c) Carbonation
(d) Organic Weathering

Answer: (b) Mechanical Weathering

4. The sudden contraction and expansion peels off the outer rock layer:

(a) Solution
(b) Exfoliation
(c) Hydration
(d) Oxidation

Answer: (b) Exfoliation

5. Reaction of minerals in rocks to atmospheric oxygen:

(a) Oxidation
(b) Solution
(c) Hydration
(d) Carbonation

Answer: (a) Oxidation

6. Which of the following occurs in moist and cold climates?

(a) Mechanical Weathering
(b) Chemical Weathering
(c) Organic Weathering
(d) Physical Weathering

Answer: (b) Chemical Weathering

7. Weathering due to the action of animals, plants and human beings is also known as:

(a) Mechanical Weathering
(b) Chemical Weathering
(c) Organic Weathering
(d) Physical Weathering

Answer: (c) Organic Weathering

8. Expansion of minerals on coming into contact with rainfall:

(a) Oxidation
(b) Solution
(c) Hydration
(d) Carbonation

Answer: (c) Hydration

9. A process in which minerals in the rocks dissolve in water:

(a) Solution
(b) Oxidation
(c) Carbonation
(d) Hydration

Answer: (a) Solution

10. Which of the following is more rapid in desert climates?

(a) Mechanical Weathering
(b) Chemical Weathering
(c) Organic Weathering
(d) Weathering

Answer: (a) Mechanical Weathering

11. In which of the following decomposition of rocks take place with changes in the chemical constituents of rocks?

(a) Weathering
(b) Chemical Weathering
(c) Organic Weathering
(d) Physical Weathering

Answer: (b) Chemical Weathering

12. In which of the following climates there is a marked dry season and wet season?

(a) Polar climates
(b) Equatorial climates
(c) Tropical climates
(d) Dry climates or deserts

Answer: (c) Tropical climates

13. The internal forces operating in the interior of the earth are called _________.

(a) Exogenic forces
(b) Endogenic forces
(c) Constructive forces
(d) Weathering forces

Answer: (c) Constructive forces

14. Tension and splitting of rocks is known as _________.

(a) Hydration
(b) Weathering
(c) Block Disintegration
(d) Solution

Answer: (c) Block Disintegration

15. In which of the following climates physical weathering due to frost action is more prevalent?

(a) Equatorial climates
(b) Polar climates
(c) Tropical climates
(d) Temperate climates

Answer: (b) Polar climates

16. Given below are different climate types with the predominant weathering action. Select which one is incorrect.

(A) Equatorial Climate – Chemical weathering
(B) Tropical Climate – Chemical weathering
(C) Dry Climate – Biological weathering
(D) Temperate Climate – Mechanical weathering
(E) Polar Climate – Mechanical weathering

(a) B
(b) C
(c) D
(d) E

Answer: (b) C

17. Melting of ice in polar regions has increased which type of weathering?

(a) Mechanical
(b) Chemical
(c) Biological
(d) All of them

Answer: (b) Chemical

Short Answer Questions

1. What is weathering?

Answer: Weathering is the process of breaking down of rock but not its removal. It is described as disintegration or decomposition of a rock in size by natural agents at or near the surface of the earth.

2. Name three types of weathering.

Answer: Weathering is of three types—physical, chemical, and biological.

3. Give two differences between physical and chemical weathering.

Answer: Two differences between physical (or mechanical) and chemical weathering are:

In physical weathering, disintegration of rocks takes place without any change in chemical constituents of rocks, whereas in chemical weathering, decomposition of rocks takes place with changes in the chemical constituents of rocks.
In physical weathering, factors such as temperature, moisture, frost action and wind cause physical break-up of rocks, whereas in chemical weathering, temperature, moisture, etc., cause minerals in rocks to either dissolve in water or change their composition.

4. What is known as exfoliation? Name the processes involved in it.

Answer: The sudden contraction and expansion of rocks, often due to sudden temperature changes, which peels off the outer layer is known as exfoliation. The processes involved include sudden temperature changes which cause fissures and the subsequent sudden contraction and expansion of the rock.

5. Name the four processes involved in chemical weathering.

Answer: The four main processes involved in chemical weathering are oxidation, carbonation, hydration and solution.

6. What is known as oxidation? What effect does it have on the colour of rocks?

Answer: Oxidation means the reaction of minerals in rocks to atmospheric oxygen. On coming in contact with iron-compounds in rocks, the iron starts rusting or crumbling. The effect it has on the colour of rocks is that the colour of the rock also changes to red, yellow or brown.

Distinguish between the Following

1. Distinguish between Block Disintegration and Exfoliation.

Answer: Block Disintegration is a process where the sudden rise and fall of temperature causes expansion and contraction of rocks. This repeated action causes their breakdown. At night the temperature suddenly falls and during the day it rises suddenly, leading to tension and splitting of rocks.

Exfoliation, on the other hand, occurs when sudden temperature changes cause fissures into which water penetrates, stimulating chemical weathering. Since most rocks are not good conductors of heat, the sudden contraction and expansion peels off the outer layer of the rock.

2. Distinguish between Carbonation and Solution.

Answer: Carbonation is a process where many mineral constituents of rocks, such as carbon dioxide, come into contact with water and produce an acidic effect on rocks. This action dissolves most calcareous rocks such as gypsum, marble, and limestone. In carbonation, rainwater converts calcium carbonate into calcium bicarbonate, which is soluble and is taken away by the ground water. This action should not be mistaken for solution.

Solution is the process in which minerals in the rocks dissolve in water. All rocks are subjected to solution to some extent. The rate at which solution takes place is affected not only by the mineral composition of the rock but also by its structure. For example, sedimentary rocks have pore-spaces between the grains in which air and water can lodge and thus attack the rocks. Some rock minerals such as salts are more soluble in water than others; for instance, rainwater causes chemical disintegration of rock-salt and gypsum.

Structured Questions

1. (a) Define weathering and describe the chief characteristics of weathering.

Answer: Weathering is the process of breaking down of rock, but not its removal. It is described as disintegration or decomposition of a rock in size by natural agents at or near the surface of the earth. It is so called because the disintegration or decomposition of rocks take place only by being exposed.

The chief characteristics of Weathering are:

Weathering involves disintegration or decay of solid rocks.
It depends on climatic elements and on the characteristics of rocks. For example, the rock’s chemical composition, hardness, texture and its permeability (allowing water to penetrate) determines the weathering pattern.
Weathering affects the surface of the earth.
Weathering causes formation of soil.
Weathering involves not one but several processes to cause disintegration of rocks.
Weathering changes hard massive rocks into finer materials.
It prepares rock materials for transportation by agents of gradation.

(b) Distinguish between physical and chemical weathering.

Answer: Physical (Mechanical) Weathering and Chemical Weathering can be distinguished as follows:

In Mechanical (Physical) Weathering, disintegration of rocks takes place without any change in chemical constituents of rocks, whereas in Chemical Weathering, decomposition of rocks takes place with changes in the chemical constituents of rocks.
In Mechanical (Physical) Weathering, factors such as temperature, moisture, frost action and wind cause physical break-up of rocks. In Chemical Weathering, temperature, moisture, etc., cause minerals in rocks to either dissolve in water or change their composition.
Mechanical (Physical) Weathering is more rapid in desert climates, while Chemical Weathering occurs in moist and cold climates.
In Mechanical (Physical) Weathering, rocks are affected to great depths. Chemical Weathering mostly takes place near the surface of the earth.
The agents of Mechanical (Physical) Weathering are temperature and moisture. The agents of Chemical Weathering are water, oxygen, carbon and various organic acids.

(c) Give a geographical reason for each of the following:
(i) Physical weathering is also called mechanical weathering.

Answer: Physical weathering is also known as Mechanical Weathering because it involves rock disintegration without any change in the chemical constituents of the rock, implying a mechanical or physical break-up process.

(ii) Physical weathering is more rapid in desert climates.

Answer: Physical weathering is more rapid in desert climates because temperature changes are sharpest in a desert. In dry climates or deserts, mechanical weathering is most dominant due to high diurnal range of temperature.

(iii) Chemical weathering occurs in moist and cold climates.

Answer: Chemical weathering occurs in moist and cold climates. For instance, in Equatorial climates, high humidity and temperature make chemical weathering more active. In polar (cold) climates, recent studies have shown that melting water contains more carbonic acid because carbon dioxide is more soluble at low temperatures, suggesting that chemical weathering is more active in these regions than previously thought.

(d) Draw a well labelled diagram to show the process of physical weathering.

Answer: See Fig. 9.2 of Morning Star/Total Geography book or click here.

2. (a) Describe chemical weathering mentioning the processes involved in it.

Answer: In chemical weathering, some or all of the minerals in the rocks suffer decay or alteration by such agents as water, oxygen, carbon or various organic acids. It leads to decomposition of rocks and minerals as chemical reaction transform them into different chemical combinations.
The chemical weathering of rocks is accomplished in a number of ways and each one is given a name to distinguish the different processes involved. Four main processes are oxidation, carbonation, hydration and solution.

(i) Oxidation: It means reaction of minerals in rocks to atmospheric oxygen. The rainwater also contains atmospheric oxygen. On coming in contact with iron-compounds in rocks, the iron starts rusting or crumbling. The colour of the rock also changes to red, yellow or brown.
(ii) Carbonation: Many mineral constituents of rocks such as carbon dioxide while coming in contact with water produce acidic effect on rocks. This action dissolves most calcarous rocks such as gypsum, marble and limestone. In the case of carbonation, rainwater converts calcium carbonate into calcium bicarbonate which is soluble and is taken away by the ground water.
(iii) Hydration: In this process, expansion of minerals occurs on coming into contact with rainwater. These minerals become heavy and start disintegrating. This action, though can be termed as physical or mechanical, its effect in hydration is a chemical process. Rocks like feldspar are converted into kaolin.
(iv) Solution: It is the process in which minerals in the rocks dissolve in water. All rocks are subjected to solution to some extent. The rate at which solution takes place is affected not only by the mineral composition of the rock but also by its structure. For example, rainwater causes chemical disintegration of rock-salt and gypsum.

(b) What is biological weathering? State the main agents of biological weathering.

Answer: Biological weathering is also known as Organic Weathering. Its main agents are animals, insects, plants and man. In all the cases, however, both physical disintegration and/or chemical decomposition are involved.

The main agents of biological weathering are:

(i) Humans: Man is the most active agent of both physical and chemical weathering of rocks. For example: mining, excavations, construction of roads, buildings, etc. cause physical disintegration of rocks. Agriculture, dumping of chemicals and wastes underground promote both physical and chemical weathering.
(ii) Plants: Roots of large trees reach deep into rocks and cause physical disintegration due to pressure.
(iii) Animals and Insects: Animals like rabbits, worms, moles and insects bring large quantities of fine material to the surface. Burrowing animals help to loosen the surface materials around the rocks facilitating their physical disintegration. Upon death, the decaying animals also provide many chemicals and acids for rock disintegration.

(c) Give a geographical reason for each of the following:
(i) Biological weathering is also known as organic weathering.

Answer: Biological weathering is also known as Organic Weathering because its main agents are animals, insects, plants, and man, which are all forms of biological or organic matter. Furthermore, all biological matter is made up of oxygen and water, the two substances that set off reaction of minerals in rocks, linking the process to organic components.

(ii) Vegetation prevents disintegration of rocks.

Answer: Most of vegetation prevents disintegration of rocks because it binds the surface layer and does not allow exposure of rocks beneath to the elements of weathering.

(iii) Chemical and biological weathering is negligible in polar climates.

Answer: In Polar climates, physical weathering due to frost action is more prevalent. Chemical and biological weathering in these areas is negligible.

(d) Describe the chief characteristics of weathering in different climates.

Answer: The chief characteristics of weathering in different climates are as follows:

(i) In Equatorial climates, humidity and temperature are constantly high. Weathering specially chemical weathering is more active in these regions.
(ii) In Tropical climates, there is a marked dry season and wet season. Differences in heating leads to consistently high rate of evaporation. During wet season, precipitation of oxides of iron and aluminium takes place from rocks. This promotes formation of laterite soils.
(iii) In Dry climates or deserts, mechanical weathering is most dominant due to high diurnal range of temperature.
(iv) In Mid-latitudes or Temperate Climates, the most powerful agent of weathering is the frost action. In limestone areas, ‘Solution’ or chemical weathering operates on a large scale.
(v) In Polar climates, physical weathering due to frost action is more prevalent. Chemical and biological weathering in these areas is negligible. However, recent studies have shown that the melting water of polar regions contains more carbonic acid content because carbon dioxide is more soluble at low temperatures than at high temperatures. This suggests that chemical weathering is more active in polar regions.

Thinking Skills

1. Weathering is a natural process, but human activities can speed it up. Do you agree with this statement? Give reasons to support your answer.

Answer: Yes, I agree that human activities can speed up the process of weathering. For instance, construction work like building roads, digging tunnels, or mining causes rocks to break apart, which is a form of physical weathering. Moreover, industrial activities release chemicals and gases that mix with rainwater to form acids. These acids then react with rocks, leading to chemical weathering. Even agricultural practices, where chemicals and fertilisers are added to the soil, can lead to both physical and chemical weathering. So, while weathering is natural, humans definitely make it happen faster.

2. It is weathering that is responsible for bio-diversity on the earth. Justify this statement giving examples.

Answer: Weathering plays a key role in the development of biodiversity. When rocks break down, they form soil, and this soil becomes the base for plants to grow. Different types of weathering produce different types of soil, each supporting various kinds of vegetation. For example, chemical weathering in tropical regions leads to the formation of laterite soil, which supports specific plant species. Biological weathering caused by roots and decaying organisms also adds nutrients to the soil. As different plants grow, they attract different animals, insects and birds, thereby increasing biodiversity in that area.

3. You went to the Rann of Kutch for the Rann Utsav, which is celebrated annually in Gujarat. On your way, which kind of weathering did you notice? What could be its cause/causes?

Answer: On my journey to the Rann of Kutch during the Rann Utsav, I observed signs of physical weathering, particularly block disintegration. This region lies in a desert climate, where the temperature during the day becomes extremely hot and drops sharply at night. These rapid changes in temperature cause the rocks to expand during the heat of the day and contract in the coolness of the night. This repeated process creates stress in the rocks, eventually causing them to crack and break into large blocks.

I also noticed features that suggested granular disintegration. Since the rocks in this region are composed of different minerals, uneven expansion and contraction during the hot and cold cycles cause the rocks to break down into smaller fragments or grains. These signs were most visible on rock surfaces and boulders scattered along the roadsides.

Although the Rann is mostly dry, any moisture that enters the cracks in rocks during cooler months can freeze at night. The freezing of water increases its volume, exerting pressure on the rock and leading to further cracking — a process known as frost action, another form of physical weathering.

These forms of mechanical weathering are typical of dry desert areas like the Rann of Kutch due to the extreme temperature variation between day and night, lack of vegetation cover, and minimal rainfall.

Practical Work

1. Collect rock samples. Perform experiments to study physical and chemical weathering. Write down your report.

Answer: Do it yourself. Here are the instructions:

Collect rocks from your garden, park or roadside. Pick 2–3 different types—smooth, rough, hard, soft.
For physical weathering:
- Place a rock in the freezer overnight, then leave it in the sun the next day. Repeat this process 2–3 times.
- Observe if it cracks or flakes. This simulates freeze-thaw action.
For chemical weathering:
- Put a small piece of limestone or chalk in a bowl of vinegar or lemon juice.
- Observe fizzing. This shows carbonation—acid reacting with calcium carbonate.
Write your report:
- Name the rocks.
- Describe what happened during each experiment.
- Mention which type of weathering occurred and why.

2. Observe the process of weathering active in your surroundings. State its chief characteristics. Draw, paint or take pictures.

Answer: Do it yourself. Here are the instructions:

Look around: Check walls, rocks, or old bricks in your neighbourhood, school, or garden.
Look for signs of weathering:
- Cracks or flaking (physical)
- Discolouration or rust (chemical)
- Plant roots breaking concrete or insects in soil (biological)
Note the type of weathering and its features:
- Is it caused by temperature change, water, roots or chemicals?
- Is the surface becoming powdery, cracked, or changed in colour?
State characteristics like:
- Rock breaking down without being moved
- Caused by natural forces
- Depends on climate and rock type
Draw or click pictures of the affected spots.
Optional: Paint a scene showing the weathering process.

Extras

Additional MCQs

1. What term describes the breaking down of rock without its removal?

A. Weathering
B. Erosion
C. Denudation
D. Transportation

Answer: A. Weathering

2. On which celestial body do footprints remain intact for millions of years due to absence of weathering?

A. Mars
B. Moon
C. Mercury
D. Venus

Answer: B. Moon

3. Weathering prepares rock materials for which subsequent process?

A. Deposition
B. Transportation
C. Solidification
D. Melting

Answer: B. Transportation

4. Which rock property influences weathering pattern by allowing water to penetrate?

A. Hardness
B. Texture
C. Permeability
D. Colour

Answer: C. Permeability

5. Which forces operating on Earth’s surface derive their energy from the sun?

A. Endogenic forces
B. Exogenic forces
C. Tectonic forces
D. Gravitational forces

Answer: B. Exogenic forces

6. In the term “exogenic forces,” what does “exo” mean?

A. Inside
B. Outside
C. Surface
D. Under

Answer: B. Outside

7. Which forces operating in the Earth’s interior are described as “constructive”?

A. Tectonic forces
B. Exogenic forces
C. Constructive forces
D. Erosional forces

Answer: C. Constructive forces

8. Which of the following is NOT a characteristic of weathering?

A. It affects the Earth’s surface
B. It involves rock disintegration
C. It results in soil formation
D. It involves removal of rock

Answer: D. It involves removal of rock

9. Which outcome is directly produced by weathering?

A. Mountain building
B. Soil formation
C. Magma generation
D. Fold creation

Answer: B. Soil formation

10. Physical weathering is also known as which of the following?

A. Chemical weathering
B. Organic weathering
C. Mechanical weathering
D. Carbonation

Answer: C. Mechanical weathering

11. Which of the following is NOT a factor responsible for physical weathering?

A. Temperature changes
B. Frost action
C. Wind
D. Carbonation

Answer: D. Carbonation

12. The splitting of rocks due to sudden expansion and contraction from temperature changes is called?

A. Granular disintegration
B. Block disintegration
C. Exfoliation
D. Frost action

Answer: B. Block disintegration

13. Which process reduces rocks into small fragments because different minerals expand at different rates?

A. Exfoliation
B. Granular disintegration
C. Block disintegration
D. Hydration

Answer: B. Granular disintegration

14. The peeling off of the outer layer of rock caused by thermal stresses is known as?

A. Frost action
B. Exfoliation
C. Carbonation
D. Oxidation

Answer: B. Exfoliation

15. The freezing and expansion of water in rock cracks that leads to rupture is called?

A. Frost action
B. Block disintegration
C. Hydration
D. Solution

Answer: A. Frost action

16. In which climate is physical weathering most rapid?

A. Equatorial
B. Desert
C. Temperate
D. Polar

Answer: B. Desert

17. Chemical weathering involves changes in which aspect of rocks?

A. Size
B. Colour
C. Chemical constituents
D. Grain shape

Answer: C. Chemical constituents

18. Which chemical weathering process involves reaction of minerals with atmospheric oxygen?

A. Carbonation
B. Hydration
C. Oxidation
D. Solution

Answer: C. Oxidation

19. Which process converts calcium carbonate into soluble calcium bicarbonate?

A. Oxidation
B. Carbonation
C. Hydration
D. Exfoliation

Answer: B. Carbonation

20. Which process involves expansion of minerals when they absorb water, as in the conversion of feldspar to kaolin?

A. Solution
B. Hydration
C. Oxidation
D. Block disintegration

Answer: B. Hydration

21. Which process refers specifically to minerals dissolving directly in water?

A. Carbonation
B. Oxidation
C. Solution
D. Exfoliation

Answer: C. Solution

22. Which rock mineral dissolves most readily in water?

A. Quartz
B. Feldspar
C. Gypsum
D. Rock-salt

Answer: D. Rock-salt

23. Biological weathering is also known as?

A. Mechanical weathering
B. Chemical weathering
C. Organic weathering
D. Exogenic weathering

Answer: C. Organic weathering

24. Which of the following is NOT an agent of biological weathering?

A. Humans
B. Plants
C. Animals
D. Wind

Answer: D. Wind

25. Which type of weathering typically affects rocks to greater depths?

A. Mechanical weathering
B. Chemical weathering
C. Biological weathering
D. Exfoliation

Answer: A. Mechanical weathering

26. Which type of weathering mostly occurs near the Earth’s surface?

A. Mechanical weathering
B. Chemical weathering
C. Biological weathering
D. Block disintegration

Answer: B. Chemical weathering

27. Which of the following acts as an agent of chemical weathering?

A. Frost action
B. Wind
C. Organic acids
D. Root pressure

Answer: C. Organic acids

28. Chemical weathering is particularly active in which climate?

A. Equatorial
B. Desert
C. Temperate
D. Polar

Answer: A. Equatorial

29. Precipitation of iron and aluminium oxides in tropical wet seasons promotes formation of which soil?

A. Laterite soil
B. Alluvial soil
C. Black soil
D. Red soil

Answer: A. Laterite soil

30. Frost action is the most powerful weathering agent in which climate?

A. Temperate
B. Equatorial
C. Tropical
D. Dry

Answer: A. Temperate

31. Which weathering process dominates in dry (desert) climates?

A. Mechanical weathering
B. Chemical weathering
C. Biological weathering
D. Solution

Answer: A. Mechanical weathering

32. Which type of weathering is negligible in polar climates?

A. Biological weathering
B. Mechanical weathering
C. Chemical weathering
D. Exfoliation

Answer: A. Biological weathering

33. The increased carbonic acid in polar meltwater suggests activity of which weathering?

A. Chemical weathering
B. Mechanical weathering
C. Biological weathering
D. Block disintegration

Answer: A. Chemical weathering

34. Which of the following is NOT a chemical weathering process?

A. Oxidation
B. Carbonation
C. Block disintegration
D. Hydration

Answer: C. Block disintegration

35. Which rock type is particularly vulnerable to solution weathering due to its pore spaces?

A. Igneous rocks
B. Metamorphic rocks
C. Sedimentary rocks
D. Volcanic rocks

Answer: C. Sedimentary rocks

36. Which process of physical weathering creates fissures that enhance chemical weathering?

A. Block disintegration
B. Granular disintegration
C. Exfoliation
D. Frost action

Answer: C. Exfoliation

37. Which of these is an agent of mechanical weathering but not of chemical weathering?

A. Wind
B. Organic acids
C. Oxygen
D. Carbon dioxide

Answer: A. Wind

38. Which natural agent can prevent rock disintegration by binding surface layers?

A. Vegetation
B. Frost
C. Wind
D. Carbonation

Answer: A. Vegetation

39. Burrowing animals and insects contribute to weathering by which action?

A. Binding soils
B. Bringing fine materials to surface
C. Dissolving minerals
D. Peeling rock layers

Answer: B. Bringing fine materials to surface

40. Which human activity causes primarily physical disintegration of rocks?

A. Mining
B. Agriculture
C. Dumping chemicals
D. Burrowing

Answer: A. Mining

41. Which human activity primarily promotes chemical weathering?

A. Excavation
B. Dumping chemicals underground
C. Road construction
D. Tree planting

Answer: B. Dumping chemicals underground

42. Carbonation in weathering involves reaction of water with which gas?

A. Oxygen
B. Carbon dioxide
C. Nitrogen
D. Sulphur dioxide

Answer: B. Carbon dioxide

43. In endogenic forces, “endo” means which of the following?

A. Inside
B. Outside
C. Surface
D. Below

Answer: A. Inside

44. Which process is NOT part of exogenic forces acting on Earth’s surface?

A. Weathering
B. Erosion
C. Volcanic activity
D. Transportation

Answer: C. Volcanic activity

45. In exogenic processes, climate acts as which of the following?

A. Driving agent
B. Constructive force
C. Denudation
D. Transportation

Answer: A. Driving agent

46. Which pair of factors primarily causes mechanical weathering?

A. Temperature and moisture
B. Water and oxygen
C. Carbon dioxide and acids
D. Root pressure and animals

Answer: A. Temperature and moisture

47. Which chemical weathering process changes rock colour to red, yellow, or brown?

A. Oxidation
B. Carbonation
C. Hydration
D. Solution

Answer: A. Oxidation

48. Which pair of processes both represent chemical weathering?

A. Oxidation and carbonation
B. Block disintegration and exfoliation
C. Frost action and wind erosion
D. Granular disintegration and frost action

Answer: A. Oxidation and carbonation

49. Which of the following is an example of biological weathering by plants?

A. Frost action
B. Root pressure
C. Oxidation
D. Hydration

Answer: B. Root pressure

50. Hydration in weathering is classified under which category?

A. Mechanical weathering
B. Chemical weathering
C. Biological weathering
D. Exfoliation

Answer: B. Chemical weathering

Additional Assertion and Reason

1. Assertion (A): Weathering involves the breaking down of rock.
Reason (R): Weathering is described as the disintegration or decomposition of a rock at or near the surface of the earth.