Weathering Processes – Physical (mechanical) agents Which set lists processes that specifically cause physical weathering or mechanical rupture of rock without chemical alteration?

Introduction / Context:
Weathering breaks down rocks at Earth’s surface. It occurs via physical (mechanical) processes that fracture or disintegrate rock and via chemical processes that alter mineral composition. Distinguishing between these helps predict landform evolution and soil formation.

Given Data / Assumptions:

• The correct answer must include only mechanical agents.
• Common mechanical agents include abrasion, salt-crystal growth (crystallization), freeze–thaw, thermal stress, and pressure release (unloading).
• Chemical weathering includes oxidation, hydrolysis, carbonation, and solution.

Concept / Approach:
Abrasion physically scrapes and grinds rock (by wind, water, ice-borne sediment). Crystallization (salt weathering) exerts wedging forces within pores as crystals grow. Pressure release removes overburden, allowing expansion and fracturing (exfoliation). In contrast, oxidation and hydrolysis are chemical reactions that transform minerals, and carbonation dissolves carbonates chemically.

Step-by-Step Solution:
Filter out any set containing chemical agents.Option (a) contains only mechanical processes: abrasion, crystallization, pressure release.Confirm that options (b) and (c) include chemical processes (oxidation, hydrolysis, carbonation) and therefore are not purely mechanical.

Verification / Alternative check:
Introductory geomorphology texts classify these processes exactly as above: mechanical in (a), chemical in (b) and (c).

Why Other Options Are Wrong:

• abrasion, oxidation, hydrolysis: includes oxidation and hydrolysis, which are chemical.
• crystallization, carbonation, thermal insolation: includes carbonation, a chemical process.
• None of the above: incorrect because (a) is entirely mechanical.

Common Pitfalls:
Thinking any weathering that changes rock appearance is chemical. Mechanical weathering changes size/shape but not mineral composition.

Final Answer:
abrasion, crystallization, pressure release