erosion (redirected from eating away)

erosion (ĭrō`zhən), general term for the processes by which the surface of the earth is constantly being worn away. The principal agents are gravity, running water, near-shore waves, ice (mostly glaciers), and wind. All running water gathers and transports particles of soil or fragments of rock (formed by weathering), and every stream carries, in suspension or rolling along its bottom, material received from its tributaries or detached from its own banks. These transported particles strike against the bedrock of the stream channel, literally grinding it away and eventually settle out along the channel or find their way to the sea. The Mississippi River is being reduced by erosion at the rate of 1 ft (30 cm) in about 9,000 years. Seacoasts are eroded by ocean waves, which detach loose or nonresistant material. Waves wear the rock by both the force of their own impact and the abrasive action of the detritus they carry. Ice can erode rocks by a freezing-thawing cycle; and ice in the form of glaciers erodes by plucking off loose rocks, by its abrasive action on the surface over which it passes, and by glacial meltwater rivers and streams. In deserts and along beaches, wind transports sand, eroding one area and depositing in another. The wind can also drive sand and other particles against rocks, abrading them. Before human modification, landmasses were probably eroding at rates close to 1 inch (2 to 3 centimeters) per 1,000 years; now rates have doubled. In the United States 30% is natural erosion, while 70% is because of human intervention. Suspended sediment from erosion is one of the world's greatest pollutants. Sediment can fill reservoirs and navigable waterways, impair wildlife habitats, increase flooding and water treatment costs, and deplete valuable topsoil. It can also concentrate harmful chemicals and bacteria. The continuous washing away of the fine rich topsoil of farmland due to poor agricultural practices is a problem in many parts of the world. Accelerated erosion from removal of acres of trees and vegetation, which diminishes the natural erosion protection, is becoming increasingly common in populated areas. Strip mining also removes vegetation and can be a localized cause of erosion. Among the methods of preventing soil erosion are reforestation, maintenance of fallow strips, terracing, underdraining, ditching, deep plowing, and plowing across slopes rather than up and down. See conservation of natural resources.

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erosion

Removal of surface material from the Earth's crust and transportation of the eroded materials by natural agencies from the point of removal. Erosion is caused by wind action, river and stream processes, marine processes (sea waves), and glacial processes. The complementary actions of erosion and deposition or sedimentation operate through wind, moving water, and ice to alter existing landforms and create new landforms. Erosion will often occur after rock has been disintegrated or altered through weathering. Moving water is the most important natural agent of erosion. Sea wave erosion results primarily from the impact of waves striking the shore and the abrasive action of sand and pebbles agitated by wave action. Erosion by rivers is caused by the scouring action of the sediment-containing flowing water. Glacial erosion occurs by surface abrasion as the ice, embedded with debris, moves slowly over the ground accompanied by the plucking of rock from the surface. Wind plays a key role in arid regions as blowing sand breaks down rock and dislodges surface sand from unprotected sand dunes. Human intervention, as by the removal of natural vegetation for farming or grazing purposes, can lead to or accelerate erosion by wind and water. See also sheet erosion.

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erosion

the wearing away of rocks and other deposits on the earth's surface by the action of water, ice, wind, etc.