Explain the different modes of soil formation.

soils are formed by either:

• Physical disintegration
• Chemical decomposition of rocks

Physical disintegration of rocks is due to the action of various agents such as expansive forces of freezing water in fissures, due to sudden changes of temperatures or due to abrasion of rocks by moving water or glaciers.This type of rock weathering takes place in very significant manner in arid climates where free, extreme atmospheric radiation brings about considerable variation in temperature at sunrise and sunset.

Erosion by wind and rain is very important factor and is a continuous event. Cracking force by growing plants and roots in voids and crevasses of rock can force fragments apart. Coarse grained soils, such as gravel and sand are formed by process of physical disintegration.

When chemical decomposition or chemical weathering of rocks takes place, original rock minerals are transformed into new miner....

soils are formed by either:

• Physical disintegration
• Chemical decomposition of rocks

Physical Disintegration:

Physical disintegration of rocks is due to the action of various agents such as expansive forces of freezing water in fissures, due to sudden changes of temperatures or due to abrasion of rocks by moving water or glaciers.This type of rock weathering takes place in very significant manner in arid climates where free, extreme atmospheric radiation brings about considerable variation in temperature at sunrise and sunset.

Erosion by wind and rain is very important factor and is a continuous event. Cracking force by growing plants and roots in voids and crevasses of rock can force fragments apart. Coarse grained soils, such as gravel and sand are formed by process of physical disintegration.

Chemical Decomposition:

When chemical decomposition or chemical weathering of rocks takes place, original rock minerals are transformed into new minerals by chemical reactions. Chemical decomposition can transform hard rock minerals into soft, easily erodible matter. The principle types of decomposition are hydration,oxidation,carbonation,desilication, and leaching. Chemical decomposition of rocks results in the formation of clayey soils.