Soil-Forming Processes – Eluviation and Bleached Layers Which process produces a pale, white-to-gray, silica-rich sublayer (commonly an ash-gray, sandy E horizon) due to strong leaching under acidic conditions?

Introduction / Context:
Soil profiles often show diagnostic horizons that reveal the dominant pedogenic process. In cool, humid, acidic environments, intense leaching can create a bleached, ash-gray horizon depleted of iron and aluminum sesquioxides and enriched in resistant silica and sand—classic evidence of podzolization/podsolisation.

Given Data / Assumptions:

• The question highlights a white-to-gray, silica-rich sublayer.
• Acidic leaching is implied, moving organo-metal complexes downward.
• We focus on the named process responsible for the bleached horizon.

Concept / Approach:
Podsolisation (also spelled podzolization/podsolisation; option spelling “podsolosation”) involves eluviation from an upper horizon (E) and illuviation to a lower horizon (Bhs/Bs). The E horizon appears pale and sandy as sesquioxides and organic coatings are leached out. Other processes—calcification (CaCO3 accumulation), laterisation (residual Fe/Al enrichment in tropics), and gleisation (waterlogging reduction)—do not produce the characteristic bleached E horizon of podzolized soils.

Step-by-Step Solution:

Verification / Alternative check:
Soil taxonomy and field guides describe Spodosols/Podzols with E horizons that are light colored and sandy due to leaching of Fe, Al, and organic matter—matching the question.

Why Other Options Are Wrong:

• Calcification: Forms calcareous accumulations, not bleached E horizons.
• Laterisation: Produces red/yellow Fe–Al rich profiles, not ash-gray layers.
• Gleisation: Waterlogged, gray-blue matrices due to reduction, not acid leaching.

Common Pitfalls:
Confusing podsolisation with laterisation because both involve strong weathering; however, their colors, chemistry, and climates differ markedly.

Final Answer:
podsolosation