2.5 - Practice Questions | Soil Genesis and Development, Lesson 2 - Processes of Weathering

Quiz

Question

Question 1: Which type of weathering creates a rusting effect on minerals?

A. Hydration

Incorrect: Addition of water into the structure of minerals does not result in rusting effect. Example: Anhydrite (CaSO4), once hydrated, changes into gypsum (CaSO4.H2O). Notice that no elements were oxidized or reduced.

B. Hydrolysis

Incorrect: Hydrolysis is not directly responsible for rusting effect on minerals. Hydrolysis changes the chemical composition and size of minerals and results in the release of elements and formation of clay and quartz.

C. Oxidation

Correct: This process changes the oxidation state of mineral components, resulting in rusting in some cases. The process can make the mineral more prone to weathering. For example, an iron (II) bearing mineral can be oxidized to iron (III), which has rusty/red features.

D. Carbonation

Incorrect: This process is not directly involved in the rusting effect. It is a process where carbonic acid, formed from water and carbon dioxide, dissolves minerals.

Looks Good! Correct: This process changes the oxidation state of mineral components, resulting in rusting in some cases. The process can make the mineral more prone to weathering. For example, an iron (II) bearing mineral can be oxidized to iron (III), which has rusty/red features.

Question

Question 2: Use Figure 2 to decide which type of weathering process will dominate in Antarctica?

A. Physical

Correct: Physical. Notice that under a cold climate environment, the dominant weathering process is physical.

B. Chemical

Incorrect: Chemical weathering is not a major factor in Antarctica, because the climate is too cold, and heat is needed for chemical weathering to occur rapidly. Hydration, hydrolysis, carbonation and oxidation processes are dependent on high temperature and moisture.

C. Biological

Incorrect: Biological weathering is not a major factor in weathering in Antarctica, because the climate is too cold for plant and microbial activities.

Looks Good! Correct: Physical. Notice that under a cold climate environment, the dominant weathering process is physical.

Question

Question 3: Use Figure 1 and the following links to decide which type of weathering process will dominate in central Africa?

View Annual Average Rainfall Map

View Annual Average Temperature Map

A. Physical

Incorrect: Physical weathering is not a major factor in weathering in central Africa, because the climate is not cold/frigid. Freezing/thawing is not present because temperature does not fluctuate, i.e., the change in temperature is small. Shrink-swell may be minimal because the moisture level is high throughout the year. Salt crystal will not grow because the abundance of moisture washes the salt down.

B. Chemical

Correct: Chemical. Notice that, under a tropical climate environment, the dominant weathering process is chemical. Under this environment, ample moisture and hot temperatures enhance chemical weathering.

C. Biological

Incorrect: Biological weathering, although present, is not a major factor in weathering in central Africa, because chemical process enhanced by the high moisture and temperature overrides the biological effect.

Looks Good! Correct: Chemical. Notice that, under a tropical climate environment, the dominant weathering process is chemical. Under this environment, ample moisture and hot temperatures enhance chemical weathering.

Question

Question 4: One of the experiments shown previously in this lesson demonstrated the hydrolysis of feldspar. How does physical weathering increase the rate of chemical weathering?

(view Figure 3)

Response

Physical weathering gradually shatters the rock into small pieces. This gives more surface area exposure to chemical weathering. The key here is surface area.

Looks Good! Physical weathering gradually shatters the rock into small pieces. This gives more surface area exposure to chemical weathering. The key here is surface area.

Question

Question 5: If calcite, a primary component of limestone rock, is only slightly soluble in water, under what environment would you expect this limestone to be dissolved?

Response

In areas where carbonation occurs (humid and warm environments), the acid formed from carbon dioxide and water, slowly dissolves the limestone.

Looks Good! In areas where carbonation occurs (humid and warm environments), the acid formed from carbon dioxide and water, slowly dissolves the limestone.

Question

Question 6: Is pressure exerted by roots on a rock structure physical or chemical weathering? Why?

Response

Tricky question. The answer is both physical and chemical weathering. Although the pressure of growing roots is physical, chemicals released by roots enhance microbiological activity. The chemical by-products of the microbial activity can gradually consume/disintegrate the rock as well.

Looks Good! Tricky question. The answer is both physical and chemical weathering. Although the pressure of growing roots is physical, chemicals released by roots enhance microbiological activity. The chemical by-products of the microbial activity can gradually consume/disintegrate the rock as well.