Question

Which one of the following is a physical weathering process?

• A. Oxidation
• B. Hydrolysis
• C. Exfoliation
• D. Carbonation

Hint:

Look for the option where no new mineral forms, only mechanical breakup of the rock.

Answer 1

The Correct Option is C

Step 1: Recall the two broad types of weathering.
Weathering breaks rock down at or near the surface, and it happens in two main ways. Physical, or mechanical, weathering breaks rock into smaller pieces without changing its chemical make-up. Chemical weathering changes the minerals themselves through reactions with water, oxygen and acids.

Step 2: Check option (A), Oxidation.
Oxidation is a chemical reaction in which minerals, especially those containing iron, react with oxygen to form new minerals such as iron oxides. This changes the chemistry of the rock, so it is a chemical weathering process, not physical.

Step 3: Check option (B), Hydrolysis.
Hydrolysis is a chemical reaction between minerals, commonly feldspars, and water, which breaks the mineral structure apart and forms new minerals like clays. This is also a chemical process.

Step 4: Check option (C), Exfoliation.
Exfoliation happens when outer layers or sheets of rock peel away from a larger rock mass, usually because of the release of confining pressure, called unloading, as overlying rock erodes away, or through repeated heating and cooling. No new minerals form here, the rock just breaks apart physically into curved sheets or slabs. This makes exfoliation a physical, mechanical, weathering process.

Step 5: Check option (D), Carbonation.
Carbonation is the reaction of carbon dioxide dissolved in water with minerals such as calcite, forming soluble bicarbonates. This is a chemical process too, common in limestone weathering.

Step 6: Final answer.
Among the four choices, only exfoliation breaks rock apart without changing its mineral chemistry, so it is the physical weathering process.
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