Soil is formed by various factors:
- The Sun heats up rocks during the day so that they expand. At night, these rocks cool down and contract. Since all parts of the rock do not contract and expand at the same rate, this results in crack formation and huge rocks break up into smaller pieces.
- Water is another factor for soil formation. Water could get into the cracks in the rocks formed due to uneven heating by the Sun. If this water later freezes, it would cause the cracks to widen. Flowing water wears away even hard rock over long periods of time. Fast flowing water often carries big and small rock particles downstream. These rocks rub against each other and the resultant abrasion causes the rocks to wear into smaller and smaller particles. The water takes these particles along with it and deposits it further down its path. Soil is thus formed in places far away from its parent-rock.
- Wind also erode rocks down. The wind also sand from one place to the other.
- Living organisms also influence the formation of soil. The lichens grow on the rock surfaces. It releases certain substances that cause the rock surface to powder down and form a thin layer of soil. Other small particles like moss, are able to grow on this surface now and they cause the rock to break up further. The roots of big trees sometimes go into cracks in the rocks and as the roots grow bigger, the crack is forced bigger.
- Thus, soil is formed like this.
- Removal of the topsoil is known as the soil erosion.
Hope you could get an idea from here.
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