Weathering: physical, chemical, and biological

Correct answer: B, an exogenic process. Geomorphic processes are commonly grouped into endogenic and exogenic processes. Endogenic processes originate inside the Earth and include forces associated with internal heat, tectonic movement, and volcanism. Exogenic processes operate at or near the surface and are driven by agents such as water, wind, ice, temperature change, and organisms. Weathering breaks down or alters rock in place at the surface, so it belongs to the exogenic group. A is wrong because endogenic processes arise within the Earth. C is not the standard geomorphic classification for weathering. D is too narrow and refers to volcanic activity, which is generally linked with internal Earth processes, not ordinary surface weathering. Remember: “exo” means outside; surface processes are exogenic.

Correct answer: C, generally it does not occur. Weathering is the breakdown, disintegration, or chemical alteration of rock at or near the place where the rock is found. The material normally remains in place after weathering. Transportation is a different step: running water, wind, glaciers, waves, or gravity carry the loosened material away. That carrying process is associated with erosion and movement, not with weathering itself. A is wrong because weathering does not always move material a long distance. B is wrong because weathering can occur on land and in many environments, not only in the sea. D is wrong because glaciers are only one possible transporting agent, and weathering is not limited to glacial regions. A useful warning is that weathering and erosion often work together, but they are not identical: weathering prepares the material, while erosion transports it.

Regolith is loose material formed by weathering of rock. Exam tip: connect regolith with soil formation.

Physical weathering involves mechanical breaking. Exam tip: size changes but chemical composition does not.

Chemical weathering can change the nature of minerals. Exam tip: treat composition change as the main sign.

Plant roots can grow in cracks and weaken rocks. Exam tip: connect activities of organisms with biological weathering.

Roots create pressure while growing and widen cracks. Exam tip: remember root pressure as a simple example.

Direct answer: Option A, physical weathering. A temperature range means repeated heating and cooling. On heating, rock minerals expand; on cooling, they contract. Different minerals may expand by different amounts, and the outer surface may heat and cool faster than the interior. Repetition creates mechanical stress, cracks, and eventually the breaking or peeling of rock without requiring a chemical change. Option A is correct because this is mechanical disintegration. Option B is wrong because carbonation is chemical weathering involving carbonic acid, usually formed when carbon dioxide dissolves in water. Option C is wrong because hydrolysis is a chemical reaction between minerals and water. Option D is wrong because organic acid action involves acids produced by organisms or decaying matter and is chemical. Hot, dry areas often show strong thermal stress because daily temperature differences can be large, but the classification depends on the mechanical action. Memory cue: temperature changes break; they do not chemically transform—physical weathering.

Repeated heating and cooling can break rocks. Exam tip: connect daily temperature range with physical weathering.

Water expands on freezing and exerts pressure on cracks. Exam tip: connect frost action with cold mountainous regions.

Salt crystals create pressure in cracks. Exam tip: remember salt weathering in coastal and arid regions.

Water and carbon dioxide form weak carbonic acid. Exam tip: connect carbonation with limestone.

In oxidation, oxygen reacts with minerals. Exam tip: remember rust-like colour in iron-bearing minerals.

Iron minerals can react with oxygen and form a rust-like colour. Exam tip: reddish-brown colour indicates oxidation.

In hydrolysis, water helps change minerals into new forms. Exam tip: understand it as chemical weathering.

In hydration, minerals may expand and weaken after taking water. Exam tip: remember water absorption.

In solution, minerals dissolve in water and weaken rocks. Exam tip: treat it as a chemical weathering process.

The direct answer is C, carbonation and solution. Limestone is mainly calcium carbonate. When rainwater absorbs carbon dioxide from the air and soil, it forms weak carbonic acid. Step by step: rainwater takes in carbon dioxide; weak carbonic acid forms; this acidic water enters cracks in limestone; calcium carbonate dissolves gradually; cracks may enlarge into caves, underground channels, sinkholes, and other karst features. Option C is correct because carbonation helps the water dissolve limestone, and solution is the actual dissolving process. Option A is wrong because earthquakes and tsunamis are sudden tectonic or marine hazards, not the usual chemical weathering processes that dissolve limestone. Option B is wrong because air pressure alone does not explain limestone dissolution. Option D is wrong because magma flow is a volcanic process and is not required for ordinary limestone weathering. Other processes can affect limestone, but C is the specific and complete pair here. Memory cue: limestone plus weak carbonic acid means carbonation and solution, often producing karst.

Moisture speeds up chemical reactions. Exam tip: connect hot and humid climate with chemical weathering.

Direct answer: Option A, physical weathering. In cold regions, water enters cracks in rock. When it freezes, it expands and pushes the crack wider; when it thaws, more water can enter. Repeated freeze–thaw cycles eventually break the rock into pieces. This is mechanical action, so it is physical weathering, also called frost action or frost wedging. Option A is correct. Option B, carbonation, is chemical weathering in which carbonic acid in water reacts with minerals such as limestone. Option C, solution, is the chemical dissolving of soluble minerals in water. Option D, oxidation, is a chemical reaction commonly involving oxygen, such as rusting of iron-bearing minerals. Freezing and thawing may occur with chemical processes, but the described repeated expansion and cracking is physically mechanical. Memory cue: frost breaks; acids and oxygen chemically change.

Cracks allow weathering agents to reach inside. Exam tip: remember joints and cracks as weak points.

Weathering is the breakdown or alteration of rocks at or near Earth’s surface. When a rock is broken into smaller pieces, the total surface exposed to air, water, oxygen, acids, and living organisms becomes larger. More exposed surface gives these agents more places to act. As a result, chemical reactions and physical breakdown can proceed more rapidly, although the exact rate also depends on climate, rock type, moisture, temperature, and biological activity.

Option C is correct because an increase in surface area can make weathering faster. It does not mean that weathering must always speed up under every condition; it means the opportunity for weathering is greater. Option B is incorrect because surface area does affect contact with weathering agents. Options A and D are clearly wrong: weathering does not necessarily stop, and a rock does not immediately become a river. Thus, smaller fragments usually weather more readily than one solid block of the same material.

Soft rocks may weaken faster due to lower resistance. Exam tip: connect rock hardness with weathering rate.

Weathering changes rock into parent material from which soil forms. Exam tip: remember soil formation begins with weathering.

Lichens can release weak acids and alter rock surfaces. Exam tip: place lichens and mosses in biological weathering.