Soil is formed by breaking down of rocks at or near the surface of earth through various physical, chemical and biological processes by various factors such as sun, water, wind and living organisms.

It occurs as follows :

1. Sun : Sun heats up rocks during the day so that they expand. At night these rocks cool down and contract, this causes cracks in the rocks.
2. Water : Rain water enters these cracks. When this water freezes, it exerts pressure on the cracks and the rocks break. Fast flowing water wears the hard rocks and carries small particles of rocks down stream.
3. Wind : Strong winds erode rocks down, which rub with each other and small particles are carried away by wind.
4. Living organisms : Lichens grow on the surface of the rock, they release certain substances that cause the rock surface to powder down and form a thin layer of soil.