- Erosion:
Erosion is the breaking down of rock materials into small particles (sediment) or into dissolved materials.
Chemical erosion slowly dissolves soluble or partially soluble rock materials. Limestone and other carbonate rocks may dissolve chemically in acidic waters.
Mechanical erosion is more common: All rocks are slowly worn away by moving sand, soil, ice, wind, and water, or by combinations of these.
Most common is erosion by water (both ocean waves and flowing rivers and streams), including the sediment borne by the water.
Erosion is the consequence of all forms of weathering (topic 69).
- SOIL:
Soil is made up of rock and mineral particles of varying sizes, mixed with groundwater and a certain amount of organic matter.
Topsoil:The top layer of soil, called Topsoil, has a high organic content and is often called Humus. It is held in place by plant roots.
Soil is churned by the burrowing activities of various underground animals and by many other species that live mostly above ground
but also burrow for safety or shade.
The action of Earthworms is particularly important because they pass soil through their digestive tracts, adding moisture and
organic matter, and leaving behind air-filled passageways
that moisten, loosen and aerate the soil to the benefit of plants and their roots.
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