Soil is the uppermost layer of the Earth's crust and is usually composed of a thin layer of mineral particles, and a layer of dead and decayed plant and animal remains called humus.
Soil is not just a layer of dirt and mud. It is actually filled with life. There are a variety of insects, reptiles, and many other animals right under our feet.
Soil also provides the vital nutrients required for plants to grow and thrive. Thus, all living organisms depend directly or indirectly on soil.
Soil formation is a slow, stepwise process and it takes thousands of years to form a layer of soil just a few centimeters thick.
It is a result of continuous breaking down of rocks by a process called weathering.
Weathering:
Weathering is the disintegration of rocks on the Earth's surface caused by exposure to natural forces such as wind, water, frost, roots of plants, etc.
Due to the physical, chemical, and biological activities that take place during soil formation, well-developed layers of soil are formed, one below the other.
Typically, four distinct soil layers can be seen, distinguishable due to differences in colour and size of the particles. These layers are referred to as horizons.
A vertical section that shows the distinct layers of soil or horizons when we cut straight down into the soil is known as a soil profile.
