Soils are formed when rocks are broken down. These rocks may be bedrock beneath the soil. They may also be rock above or within the soil called parent material.
These rocks are broken down through a process called weathering. There are two primary categories of weathering:
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The expansion and contraction of water as it freezes and thaws. The activity of living matter such as plant root growth, lichen waste deposition, and the activity of animals. The abrasive action of material passed over the rock by motion due to wind, water, gravity, or the movement of animals. |
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Reactions which dissolve all or part of the rock material. This occurs with a variety of solvents including water, acids produced by living matter and deposited by acid precipitation, and oxygen. |