Soil formation involves the buildup of parent material, the release of simple compounds, the accumulation of organic matter, the collection of humus from dead plants and the process of leaching. These processes lead to the creation of different soil layers called horizons.
All soils originate from a parent material, which is a deposit at the surface of Earth. Parent materials can be weathered bedrock or small materials brought by strong winds, flowing rivers or moving glaciers. The simple compounds released by weathering become food sources for soil organisms, such as bacteria and fungi. The remains of the dead organisms accumulate in the parent material and turn into organic matter, or humus.
The soil continues to develop and starts to support higher plant and animal life forms, whose activity causes changes in the humus level in the soil. The dead plant material builds up in the loose parent material’s upper layers. The soil pH lowers, and leaching occurs, in which percolating waters remove materials from the soil.
Precipitation, organic matter and solar energy contribute to an increase in soil size. Some of the damaging processes that affect soil include erosion, nutrient leaching and water loss through plant transpiration. Plants perform nutrient cycling, and organisms mix soil, causing the materials in the soil to move. Lastly, the soil gains new compounds from organic material and weathered rocks.