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    Geomorphic Processes
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    How mechanical weathering takes place in cold and hot regions ? Describe.
    Mechanical weathering, which is responsible for the disintegration of rocks without changing their chemical composition is brought about by the changes in temperature in hot regions and freezing action by water in cold regions.

    Weathering in Cold Regions : Weathering in the cold regions take place due to the action of freezing water. In these regions, water in the cracks or joints in rocks freezes and it increases its volume and the rock requires more space which cause a progressive widening of the cracks in rock and the rock is ultimately split into pieces or blocks. It is also known as frost weathering.

     


    Weathering in Hot Regions :     Weathering in hot regions, particularly in deserts take place due to temperature changes. In these regions, the bare rocks are heated and get expanded. Different minerals which constitute the rock react to the heat differentially. The rate of expansion and contraction of these minerals differs. As a result, cracks and joints develop in the rock layers which ultimately split it up into angular blocks of fragments or grains.

    The alternate expansion and contraction of outer rock layers is more than the inner layers. The outer layers are peeled off from the main mass of the rock in the form of concentrate slide. This kind of weathering is call ex-foliation.
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    Describe the processes involved in chemical weathering.
    Chemical weathering is achieved through following four processes :



    1. Oxidation : In it the atmospheric oxygen combines with minerals of rocks. With the result, the rocks get rusted, as, iron is rusted due to the presence of air and water. Original colour changes into red, yellow or brown. The rock begins to decay and becomes a powdered dust.


    2. Hydration : The chemical reaction of water with aluminium bearing minerals detaches the outer shell of such rocks through the process of hydration. Feldspar is reduced to kaolin through hydration.


    3. Carbonation : Rainwater mixed with carbon dioxide is slightly acidic. It dissolves limestone, chalk and marble rocks.


    4. Solution : Some of the minerals like rock salt and gypsum are dissolved in water. These minerals are dissolved in solution from the rocks.

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    What are soils ?

    Soils are products of a complex mixture of weathered and eroded rock material on the one hand and the organic matters on the other.
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    What is humus?
    The decomposition of plants and microorganisms releases organic chemicals that interact with the loose materials is called humus. It is the dead organic matter in the soil.
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    Describe soil texture.
    Soil texture 

    (i) It is a qualitative classification tool used in both the field and laboratory to determine classes for agricultural soils based on their physical texture.

    (ii) The classes are distinguished in the field by the "textural feel" which can be further clarified by separating the relative proportions of sand,silt and clay using grading sieves:  

    (iii) The class is then used to determine crop suitability and to approximate the soils responses to environmental and management conditions such as drought or calcium (lime) requirements
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