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Difficulty: MediumRocks, Minerals, and Soil

Weathering breaks down rock materials at or near Earth's surface through distinct mechanical and chemical mechanisms. Match each weathering process with its correct scientific description.

  • Frost wedgingWater seeps into rock fractures, expands as it freezes, and exerts mechanical stress that widens cracks.
  • HydrolysisSilicate minerals such as feldspar react with water and dissolved hydrogen ions to chemically decompose into clay minerals.
  • ExfoliationThe removal of heavy overlying rock relieves confining pressure, causing outer crystalline rock layers to fracture and peel in sheets.
  • CarbonationDissolved carbon dioxide in rainwater creates a weak acid that reacts with calcite to chemically dissolve limestone bedrock.

Answer

Frost wedging matches the process where water enters rock cracks and expands upon freezing; Hydrolysis matches the chemical breakdown of silicate minerals into clays by reaction with water ions; Exfoliation matches the peeling and fracturing of outer rock layers due to the release of overlying confining pressure; Carbonation matches the reaction of weak carbonic acid with carbonate minerals to dissolve rock.
Each weathering mechanism corresponds to a distinct geological agent: frost wedging uses the physical expansion of freezing ice; exfoliation relieves confining tectonic/lithostatic pressure to split outer slabs; hydrolysis chemically hydrates and alters feldspars into clays; and carbonation utilizes carbonic acid to dissolve carbonate rocks such as limestone.

Step-by-Step Solution

1
Classify each term by whether it operates as mechanical (physical) weathering or chemical weathering.
Frost wedging and exfoliation are mechanical weathering processes; hydrolysis and carbonation are chemical weathering reactions.
Categorizing the fundamental breakdown mechanism narrows down matching definitions based on physical stress versus chemical alteration.
2
Distinguish between the physical mechanisms of frost wedging and exfoliation.
Frost wedging involves thermal freeze-thaw cycles expanding trapped water, while exfoliation involves pressure release (unloading) causing curved surface sheets to slough off.
Isolating the specific physical driver ensures accurate matching of mechanical processes.
3
Distinguish between the chemical mechanisms of hydrolysis and carbonation.
Hydrolysis specifically alters silicate minerals (like feldspar into clay) through direct water reaction, whereas carbonation involves carbonic acid reacting with carbonate minerals (like calcite in limestone) to cause dissolution.
Differentiating the reacting chemical species and target mineral groups prevents misidentifying chemical processes.

Key Concept

Mechanical versus chemical weathering processes and their specific geological mechanisms.
Estimated Time:1m 15s
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Topics

Rocks, Minerals, and Soil

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