Weathering ~ by Hamdsome Wu ~

Weathering
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Weathering is the decomposition of earth rocks, soils and their minerals through direct contact with the planet's atmosphere[1]. Weathering occurs in situ, or "with no movement", and thus should not to be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, wind, and gravity
Two important classifications of weathering processes exist. Mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions such as heat, water, ice and pressure. The second classification, chemical weathering, involves the direct effect of atmospheric chemicals, or biologically produced chemicals (also known as biological weathering), in the breakdown of rocks, soils and minerals.
The materials left over after the rock breaks down combined with organic material creates soil. The mineral content of the soil is determined by the parent material, thus a soil derived from a single rock type can often be deficient in one or more minerals for good fertility, while a soil weathered from a mix of rock types (as in glacial, eolian or alluvial sediments) often makes more fertile soil.
Mechanical weathering is the cause of the disintegration of rocks. The primary process in mechanical weathering is abrasion (the process by which clasts and other particles are reduced in size). However, chemical and physical weathering often goes hand in hand. For example, cracks exploited by mechanical weathering will increase the surface area exposed to chemical action. Furthermore, the chemical action at minerals in cracks can aid the disintegration process.