Geography

Soil formation processes

Q: Accumulation of clay and iron compounds in the B horizon is linked with which process?

Illuviation The governing soil-formation concept is the movement and deposition of materials between soil horizons. Illuviation is the process in which materials washed or transported downward from an upper horizon accumulate in a lower horizon, commonly the B horizon. Clay particles and compounds of iron and aluminium may be carried downward by percolating water and deposited there, making the B horizon a zone of accumulation. Eluviation is the contrasting removal process that usually affects an upper horizon such as the E horizon. Evaporation, seismic waves and marine erosion do not describe this soil-profile movement. Therefore option A is correct.

Q: Gleying is dominant under what type of soil condition?

A long-term water-saturated and low-oxygen condition Correct answer: A, a long-term water-saturated and low-oxygen condition. Gleying is a soil-forming process associated with prolonged waterlogging and poor drainage. When soil pores remain filled with water, air cannot circulate easily and oxygen becomes limited. This creates reducing conditions, which affect the form and colour of minerals such as iron compounds and may produce greyish or bluish features in the soil. A is correct because persistent saturation and oxygen deficiency are the essential conditions. B is wrong because extreme dryness does not create waterlogging or reduction. C is wrong because gleying is not defined by a volcanic eruption. D is wrong because a sandy sea surface is not the same as a waterlogged soil profile. Memory cue: gleying means grey, poorly drained, oxygen-poor soil; connect it with prolonged saturation.

In this Class 11 Geography topic from Geomorphic Processes, students learn how soil develops through the weathering of rocks and the gradual interaction of parent material, climate, organisms, relief and time. The topic explains key processes such as the addition and loss of materials, transformation of minerals and the movement of clay and other substances within the soil profile. It also helps students understand soil horizons, profile development and the influence of erosion and drainage on soil formation.

Hard · Level 7 · 2 questions

Practice questions

01Accumulation of clay and iron compounds in the B horizon is linked with which process?

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Answer and explanation

Correct answer: A. Illuviation

The governing soil-formation concept is the movement and deposition of materials between soil horizons. Illuviation is the process in which materials washed or transported downward from an upper horizon accumulate in a lower horizon, commonly the B horizon. Clay particles and compounds of iron and aluminium may be carried downward by percolating water and deposited there, making the B horizon a zone of accumulation. Eluviation is the contrasting removal process that usually affects an upper horizon such as the E horizon. Evaporation, seismic waves and marine erosion do not describe this soil-profile movement. Therefore option A is correct.

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02Gleying is dominant under what type of soil condition?

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Answer and explanation

Correct answer: A. A long-term water-saturated and low-oxygen condition

Correct answer: A, a long-term water-saturated and low-oxygen condition. Gleying is a soil-forming process associated with prolonged waterlogging and poor drainage. When soil pores remain filled with water, air cannot circulate easily and oxygen becomes limited. This creates reducing conditions, which affect the form and colour of minerals such as iron compounds and may produce greyish or bluish features in the soil. A is correct because persistent saturation and oxygen deficiency are the essential conditions. B is wrong because extreme dryness does not create waterlogging or reduction. C is wrong because gleying is not defined by a volcanic eruption. D is wrong because a sandy sea surface is not the same as a waterlogged soil profile. Memory cue: gleying means grey, poorly drained, oxygen-poor soil; connect it with prolonged saturation.