Image: Weathering


Weathering, in geology, processes of physical disintegration and chemical decomposition of solid rock materials at or near the earth`s surface. Physical weathering breaks up rock without altering its composition, and chemical weathering decomposes rock by slowly altering its constituent minerals. Both processes work together continuously to produce debris that is then transported away mechanically or in solution ( "see "Erosion). Weathering processes also aid in the formation of soil.

Physical weathering results primarily from

Physical weathering results primarily from temperature changes, such as intense heat; the action of water freezing in rock crevices; and living organisms, such as tree roots and burrowing animals. Temperature changes alternately expand and contract rocks, causing granulation, flaking, and massive sheeting of the outer layers. Frost action and organisms widen cracks, exposing deeper layers to chemical weathering.

Chemical weathering alters the original

Chemical weathering alters the original mineral composition of rock in a number of ways, such as by dissolving minerals by water and weak soil acids; by oxidation ( "see "Chemical Reaction); by producing a reaction with carbon dioxide; and by hydration, which is a process in which water chemically combines and reacts with minerals. Plants, such as lichens, also decompose certain rocks by extracting soluble nutrients and iron from the original minerals.
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"See also "Geomorphology.

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