Relief, nature of parent rock or bedrock, climate, vegetation and other forms of life, especially decomposers, and time are important factors in the formation of soil. Weathering of the parent rocks due to climatic factors like change of temperature, wind and frost action and rainfall and natural forces like action of running water, wind, glaciers etc., lead to disintegration of rocks.This leads to the formation of soil. The four most important factors of soil formation are thus : (i) Relief determines the nature of weathering and erosion. (ii) Climate determines the rate and factor of denudation of the rocks and influences weathering and erosion. (iii) Nature of the parent rock determines the colour, texture and mineral content of the soil. (iv) Time determines maturity of the soil, usually it takes millions of years to form soil upto few cms in depth.