explanation of mineral riches in soil biology of class 9 CBSE chapter-Natural Resources
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Soil is the thin layer of loose material covering the earth’s surface. It is composed of both organic and inorganic materials. The formation of soil is an extremely long process taking up to an average of a thousand years. Soil is formed when surface rocks break into several smaller particles, called regolith, which then gets mixed with varied organic matter. This whole process is called Weathering. So weathering happens through three major ways, namely
Physical Weathering: This is the geological process when rocks get fragmented into smaller particles, without changing the chemical composition of the rocks. This primarily happens due to fluctuating temperatures causing the rocks to break apart.
Chemical Weathering: This is the erosion of rocks and other surface materials caused due to chemical reactions. The rocks react with substances in the atmosphere, such as moisture, air, water etc. The resulting substance has a different chemical composition than the rock from which it formed. Hydration, Hydrolysis, Oxidation, Carbonation and Reduction are the chemical processes involved in chemical weathering.
Biological Weathering: This is the process of disintegration of rocks due to actions of living organisms (animals, plants, microbes etc), like when a plant grows in the fissure of a rock and its roots exert pressure on the rock forcing in to break apart. Even microbes produce organic material that causes weathering.