Weathering: physical, chemical, and biological

Correct answer: B. Their chemical composition may change

Chemical weathering can form new minerals or soluble substances. This separates it from physical weathering.

Correct answer: A. Because they remain in direct contact with heat

Correct answer: A, because outer layers are in direct contact with changing heat conditions. Rock surfaces receive heating and cooling before the deeper interior. During strong heating, the outer part expands; during cooling, it contracts. Repeated expansion and contraction create stress, especially near the surface. Over time, cracks may develop parallel to the surface and thin sheets can peel or break away. This is thermal or exfoliation weathering, a physical process because the rock is broken without necessarily changing its minerals chemically. B is wrong because outer rock layers are not always underwater, and submergence is not the basic cause here. C is wrong because thermal weathering does not require rocks to become magnetic. D is wrong because fossil formation is a biological and sedimentary process, not the explanation for temperature stress. Memory cue: surface heats first, expands first, cools first, and contracts first.

Correct answer: B. Oxidation and hydrolysis

Oxidation and hydrolysis can both change the chemical composition of minerals. Other options include physical or biological processes.

Correct answer: C. Roots growing in cracks and exerting pressure

Roots are living sources, but their pressure causes mechanical breaking. Such examples show a combined effect.

Correct answer: B. New cracks and more surface area are formed

Smaller pieces increase surface area, allowing more water, air, and reactions. Initial breaking can therefore speed later weathering.

Correct answer: A. Coastal or arid areas with moisture and evaporation

Crystals form when salt-rich water evaporates. This process can be common in coastal and arid areas.

Correct answer: B. Activities of organisms break or alter rocks

In biological weathering, plants, bacteria, lichens, and organisms affect rock. It can help mechanically or chemically.

Correct answer: A. Rainwater with carbon dioxide and presence of limestone

Water with carbon dioxide forms carbonic acid and dissolves limestone. Water and carbonate rock are important for carbonation.

Correct answer: B. Because different minerals have different stability and solubility

Some minerals dissolve or alter quickly, while others are more resistant. Mineral composition helps determine weathering rate.

Correct answer: C. Rock breaking due to expansion of freezing water in a crack

Expansion of freezing water breaks rock mechanically. Mineral composition does not mainly change here.

Correct answer: A. By excavating land and exposing roots or surfaces

The direct answer is A: excavation can expose roots, rock surfaces, and cracks, increasing weathering. Weathering happens when exposed rock is broken or chemically changed by water, air, temperature variation, ice, salts, or living organisms. Human activity changes the protective cover of land. The reasoning is: digging or construction removes soil and vegetation; fresh surfaces and cracks become exposed; water and air enter them; roots may grow into cracks and push against their sides; heating, cooling, and moisture act more strongly; weathering becomes more likely. Option A is correct because excavation and construction create or expose surfaces where biological and mechanical weathering can operate. Option B is wrong because humans cannot stop the Sun through ordinary land-use activity, and this has no connection with the process. Option C is wrong because excavation does not reduce gravity; gravity remains essentially the same and is not the stated cause here. Option D is wrong because making the sea solid is impossible in this context and is unrelated to weathering. A useful memory cue is: digging opens the rock, and exposure gives weathering agents access. Human actions do not create every weathering process, but they can make natural processes faster.

Correct answer: B. Physical chemical and biological

Weathering is generally studied as physical, chemical, and biological types. Remembering the classification helps identify examples quickly.

Correct answer: C. Oxidation

In oxidation, oxygen reacts with minerals, especially iron-bearing minerals. It is chemical weathering.

Correct answer: A. Because water can enter deeper and react

In permeable rock, water enters more easily. Chemical reactions with water can occur on more surfaces.

Correct answer: A. Parent rock breaking into smaller particles

Weathering can turn rocks into smaller particles and altered minerals. It is an early step in surface transformation.

Correct answer: B. Surfaces and pathways for chemical weathering will increase

Cracks create fresh openings and increase the area of rock that can come into contact with water. When acidic water enters these openings, it can react with susceptible minerals along the crack walls. Thus, physical weathering can prepare the rock for faster chemical weathering. The two processes often work together rather than acting as completely separate events.

Option B follows directly from this sequence: first the cracks provide pathways, and then acidic water uses those pathways to reach more rock. Chemical reactions can therefore occur over a larger accessible surface. Option A is opposite to the likely result, while option C ignores the purpose of cracks. A rock does not instantly become a fossil, so option D is unrelated. The speed still depends on acidity, minerals, moisture, and temperature.

Correct answer: A. Uneven dissolution and alteration of minerals

A rock surface can become pitted or weak when its minerals do not respond to weathering at the same rate. Some minerals may dissolve relatively quickly, while others may alter more slowly or resist dissolution. This uneven removal leaves small hollows, rough patches, and zones of weakness on the surface. Water, oxygen, acids, and changes in temperature can influence these reactions, but the important idea in this question is the unequal weathering of different minerals.

Option A is correct because uneven dissolution and mineral alteration can produce a pitted or weakened layer. A change in Earth’s orbit does not directly create such a surface texture, and a river does not normally flow backward. The Moon cannot fall onto the rock in the stated way. The scientifically relevant process is differential weathering, in which mineral composition and resistance cause some parts of the rock to deteriorate faster than others.

Correct answer: B. Water can assist physical chemical and biological processes

Water can freeze and expand, dissolve materials, and support organisms. Therefore it is important in many types of weathering.

Correct answer: A. Chemical weathering is more active in warm humid areas

Warm humid climate speeds chemical reactions. In climate-based questions, consider temperature and moisture together.

Correct answer: B. In-place physical breakdown chemical alteration or biological effect on rocks

Weathering can include in-place breakdown, alteration, and biological effects. Distinguish it from erosion and deposition.

Correct answer: A. Because they are more exposed due to greater surface area

Corners and edges are exposed to weathering from several directions. Therefore the rock may gradually become rounded.

Correct answer: B. Internal stress and microcracks can form

Different minerals expand and contract differently with temperature. This can increase microfracturing in physical weathering.

Correct answer: A. It can weaken minerals and increase dissolution and alteration

Acids formed from decaying organic matter can chemically affect minerals. Remember this in vegetated areas.

Correct answer: A. It is loose weathered material lying above parent rock

The direct answer is A: regolith is the loose, weathered material lying above the solid parent rock. Weathering breaks rocks into smaller pieces and may also change their minerals. The resulting cover can contain rock fragments, mineral particles and partly formed soil; this unconsolidated layer is called regolith. Option A is correct because it gives both essential ideas: loose material and its position above the parent rock. Option B is wrong because ocean depth is a measurement of seawater, not a weathering cover. Option C is wrong because hot volcanic gas is not a layer of broken rock. Option D is wrong because a glacier’s centre has no such meaning in geomorphology. Regolith may later support soil and plants, so it is important in soil formation. Memory cue: regolith means the loose rocky blanket over bedrock.

Correct answer: A. Because hard and soft rocks weather at different rates

Resistant rocks weather slowly while weaker rocks weather faster. Therefore differences in relief and depressions may appear in landforms.