What is Soil?
Soil is the upper layer of earth in which plants grow. It is a black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles.
Why is soil important?
The food chain on earth begins from plants. These plants use the water and nutrients from the soil to grow. Thus, without soil, the plants will not be able to survive and therefore the food chain of the earth will be disturbed. Soil is also useful as a home for many living organisms.
Many small organisms like ants, earthworms, etc. reside in the soil. Along with these animals, soil also acts as a shelter for the roots of plants.
Which are the weathering processes that help in the formation of soil?
Weathering is the process that changes solid rock into sediments or soil.
Over long periods of time, thousands and millions of years, the rocks at or near the surface of the Earth are broken down by various weathering processes.
Let us now look at these processes one by one.
- Physical weathering: Physical weathering is a process that causes the disintegration of rocks without chemical There are many agents that contribute to physical weathering of rocks. Let us look at a few of them.
- Sun: The Sun heats up rocks during the day which causes them to expand. At night, these rocks cool down and Since all parts of the rock do not expand and contract at the same rate, it results in the formation of cracks and ultimately the huge rocks break up into smaller pieces.
- Water: Water helps in the formation of soil in two
- The first way is when water gets in the cracks of the rocks formed due to uneven heating by the sun. If this water later freezes, it would cause the cracks to widen and ultimately break into smaller
- Fast flowing water often carries big and small particles of rocks. These rocks rub against other rocks and the resultant abrasion causes the rocks to wear down into smaller particles.
- Chemical weathering: When the disintegration of rocks is caused by chemical reactions (chiefly with water and substances dissolved in it) rather than by mechanical processes, we call it as Chemical weathering.
The most common types of chemical reactions that induce chemical weathering are:
- Oxidation
- Hydrolysis
- Hydration
- Carbonation
- Reduction
- Biological weathering: Biological weathering refers to weathering caused by organisms like animals, plants, fungi and microorganisms such as
For instance,
When the lichens grow on the surface of rocks, they release certain substances that cause the rock surface to powder down and form a thin layer of soil.
The roots of big trees sometimes make their way inside the cracks of the rocks and as the roots grow bigger, the crack widens causing them to break.