How Do Soils Form?

Soil forms continuously, but slowly, from the gradual breakdown of rocks through weathering. Weathering can be a physical, chemical or biological process: physical weathering—breakdown of rocks from the result of a mechanical action.

How Do Soils Form?

Soil is an important resource that every living creature needs to survive. It is a complex mixture of minerals, organic matter, living organisms, gases, liquids and other elements that form a thin layer of the Earth’s surface. Soils form over hundreds or even thousands of years through the breakdown of rocks and other material by natural processes.

The first step in the formation of soils is the weathering of rocks. Weathering is the breakdown of rocks and minerals into smaller particles by the action of physical, chemical, and biological agents. Physical weathering is caused by the expansion and contraction of rocks due to temperature changes, as well as the freezing and thawing of water. Chemical weathering includes the dissolution of minerals by acids such as carbonic acid. Biological weathering is caused by living organisms, such as plants and animals, that help break down the rocks into smaller particles.

After the weathering of rocks, the next step in the formation of soils is the accumulation of organic matter. Organic matter includes dead plants and animals, as well as their waste products. These materials are broken down by bacteria and other microbial organisms into smaller pieces, which are then mixed with the weathered rocks. This process is known as humification.