Soil Formation


 
 
Concept Explanation
 

Soil Formation

Soil Formation :  The uppermost layer of the Earth surface is called soil. It is usually composed of a thin layer of minerals which include sand, mud, and rock particles, and a layer of dead and decayed plant and animal remains called humus.

Soil formation is a slow, stepwise process. It takes thousands of years to form a layer of soil just a few centimetres thick. It is a result of continuous breaking down of rocks by a process called weathering.

Factors affecting Soil Formation :  There are a number of factors which affect soil formation, namely, climate, characteristics of the parent rock, and slope of land.

  • Climate: Climatic factors or weathering forces such as temperature, rain, wind, etc., play an important role in loosening and breaking up rocks (physical weathering).
  • Water in rock crevices expands when it freezes, hence, increasing the pressure and causing the rocks to crack. Rocks are also worn down by wind. Soil formation is fastest in hot, moist climates and slowest in cold, dry climates. In the warm and wet tropics, bacterial activity is high. As a result, soil in these areas have a rich content of humus. On the other hand, desert regions have very little vegetation and animal life, and so limited decaying material is available for the soil. The lack of rainfall leads to the formation of coarse-textured soil in dry and arid regions. In areas that experience severe winter, bacterial activity is very slow causing dead plant and animal matter to build up.
  • Therefore, soil in such places forms very slowly. Thus, the rate of soil formation and the type of soil formed depends on the climate of a place.
  • Characteristics of the parent rock: The composition of the parent rock also determines the kind of soil formed. For example, if the parent rock is rich in calcium, the soil formed by its weathering would be rich in calcium, too.
  • Slope of land: The physical features of a place play an important role in the formation of soil. Hilly areas generally have a thin layer of soil because running water and wind tend to carry the soil down the slope.
  • On flat plains, soil remains relatively undisturbed leading to the formation of a thick layer.

                                    

    Sample Questions
    (More Questions for each concept available in Login)
    Question : 1

    define weathering?

    Right Option : A
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    Question : 2

    _____________________ is usually present as a thin film around the soil particles.

    Right Option : C
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    Question : 3

    Humus refers to the :

    Right Option : C
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