We will discuss about the different layers of soil and their formation. We know plants grow and depend on soil. Animals depend on plants and we depend on plants and animals both. Thus all the living things depend on soil. No life is possible on the earth without soil.
Soil is not only needed for plants but we too use it for so many things, like building kachcha houses, making clay utensils clay-toys, bricks etc.
Our earth is composed mainly of soil. There are three main layers of soil. If we dig deep into the ground the layers may be differentiated. The top-layer of the soil, about 25 cm deep is dark in colour, soft and full of manures. Plants grow in this layer. It is called top-soil.
Just below the top-soil there is sub-soil. It is light coloured layer. This layer is thick and full of sand and gravels. The bottom layer is called bed-rock as it is made of solid rocks.
Soil is formed from rocks. The rocks get heated in day time by the sun and they cool at night. Due to repeated heating and cooling the rocks crack and break into small pieces. These small pieces further break into tiny pieces due to the flowing water of rivers and rivulets. The tiny pieces are transported to far off places by river water and wind. In due course the tiny pieces are turned into powder and soil is formed. Decayed plants and dead animals mix with the soil and form humus. Rotten dung, leaves of plants and other such things increase the humus in the soil.