What Is Soil


We do know that an estimated 70 percent of the earth’s surface is covered with water, while the remaining 30 per cent constitutes land. The layer of earth that is composed of soil and is influenced by the process of soil formation is called pedosphere. But what exactly is soil and what is soil made of?

What is Soil?

Technically, soil is a mixture that contains minerals, organic matter, and living organisms. But broadly speaking, soil can refer to any loose sediment. Moreover, there are many types of soil that are distributed around the world and these are generally classified into the following:

  1. Clay Soil
  2. Sandy soil
  3. Loamy Soil
  4. Silt Soil

Typically, soil consists of 45% minerals, 50% empty spaces or voids and 5% organic matter. Furthermore, soil performs many important functions such as:

  1. Providing a growth medium for the plants
  2. Acts a modifier of the earth’s atmosphere
  3. One of the most crucial components of the biosphere
  4. Provides habitat for organisms

How is Soil Formed?

Essentially, soil is formed when rocks eventually weather away and break down into small particles. Solid rock can weather away one of the two ways into soil, namely:

  1. Mechanical Weathering
  2. Chemical Weathering

Mechanical Weathering

This is commonly observed near the surface of the earth. Also called physical weathering, as this process is influenced by physical forces such as wind, water and temperature.

Chemical Weathering

As the name suggests, chemical weathering occurs when rocks are broken down by chemical reactions. Often, such types of weathering can change the chemical composition of soil.

Biological Weathering

Though not an actual weathering process, living organisms weaken and subsequently disintegrate rocks, often by initiating mechanical or chemical weathering. For instance, tree roots can grow into cracks in the rock, prying them apart and causing mechanical fractures. Microorganisms can secrete chemicals that can increase the rock’s susceptibility to weathering.

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