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Difficulty: HardSoil Formation, Profiles, and Major Vegetation Types

Along a topographical slope (soil catena), permanent waterlogging in the low-lying valley bottom causes severe oxygen depletion. This anaerobic environment leads to the biochemical reduction of ferric iron compounds into ferrous iron, imparting a distinct sticky, greyish-blue appearance to the soil profile. Which pedogenic process is responsible for this soil transformation?

  1. GleizationAnswer
  2. B
    Mechanical weathering
  3. C
    Metamorphic recrystallization
  4. D
    Mass wasting

Answer

Gleization is the pedogenic process operating under anaerobic, waterlogged conditions that converts ferric iron to ferrous iron, producing greyish-blue soil profiles.
The process described is gleization (also known as gleying). It occurs in hydromorphic soils where saturated, anaerobic conditions prevent normal oxidation. Anaerobic bacteria reduce ferric compounds (Fe3+Fe^{3+}) to ferrous compounds (Fe2+Fe^{2+}), which imparts a characteristic bluish-grey or mottled color to the soil horizon.

Step-by-Step Solution

1
Analyze the environmental conditions described in the stem.
Identified permanent waterlogging, oxygen deficiency (anaerobic environment), and low-lying topography at the base of a catena.
Water displacement of soil air suppresses aerobic decomposition and oxidation.
2
Determine the chemical reaction resulting from anaerobic conditions.
Redox state shifts from oxidation (Fe3+Fe^{3+} ferric, reddish) to reduction (Fe2+Fe^{2+} ferrous, greyish-blue).
Anaerobic microorganisms use ferric iron as an electron acceptor in place of oxygen.
3
Identify the matching pedogenic term.
Gleization (or gleying) specifically defines this process of soil development under waterlogged, reducing conditions.
Other processes listed refer to rock disintegration, metamorphism, or gravitational slope transport.

Key Concept

Pedogenic processes and Soil Catena dynamics
Estimated Time:1m 30s
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Topics

Soil Formation, Profiles, and Major Vegetation Types

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