Soil Formation
Soils are formed by either physical disintegreation or chemical decomposition od rocks. Physical Distintegration. Physical disintegration or mechanical decomposition weatheringof rocks occurs due to the following physical processes : Temperature changes. Different minerals of a rock have different cofficint of thermal expansions. Unequal expansion and contractions of these minerals occure due to temperature changes. when the stresses induced due to such changes are repeated many times, the particles get detached from the rocks and the soils are formed. wedging action of ice. water in the pores and minute cracks of rocks gets frozen in very cold climates. As the volume of the ice formed is more than that of water, expansions occurs. Rocks get broken into pieces when large stresses develop in the cracks due to wedging action of the ice formed. spreading of roots of plants. As the roots of plants and shrubs grow in the cracks and fissures of the rocks, forces act on the rock.