How is soil formed?

The uppermost layer of earth’s crust is known as soil. Weathering of rocks, metamorphosis, and chemical processes leads to formation of soil. Thus soil can be called rock in its final state of decay. Soil formation is a very slow process which can even take thousands of years. Soil which is found lying in the original place of its formation is called sedentary soil; whereas, the ones that are carried from other sites by various natural agents are called transported soil.

Early stages of formation
Molten magma that accumulated on the earth’s surface cooled and formed igneous rocks. Then erosion and weathering of rocks began. Due to weathering rocks broke down into small pieces and mingled with organic matters. Over time a thin layer of soil got formed. When the herbivorous animals die and their bodies decay, the decayed matters add to the thickness of soil and enrich it. This process goes on till soil formation becomes complete.

Soil layers
Soil formation begins at the topmost layer of surface of earth but it works differently in the layers beneath. The uppermost surface which gets maximum exposure to changes differs radically from the layers of soil, also called horizons, which lie below this bed. These horizons vary in terms of color texture and structure. The horizons from top to bottom are named as O horizon, A horizon, E horizon, B horizon and C Horizon respectively.

Factors helping soil formation

• Weathered bedrock and natural agents that carry out transportation of soil.

• Climate helps in soil formation. Temperature and moisture content directly affect weathering and leaching. The quantity and type of precipitation has a direct influence on soil formation.

• Biological factors such as plants, fungi, bacteria, animals and human beings too affect soil formation, directly and indirectly.

• Last, but not the least, time contributes in the development as well as formation of soil.