Erosion Processes See Also Reference

A certain amount of erosion is natural and in fact is fact healthy for the ecosystem. For example, gravels continually move downstream in watercourses. Too much erosion, however, can cause problems, clogging streams with gravel, filling reservoirs with sediment, reducing soil fertility and water quality.

What causes erosion to be severe in some areas and minor elsewhere? It is a combination of many factors, including the amount and intensity of precipitation, the texture of the soil, the steepness of the slope, and ground cover (from vegetation, rocks, etc.).

The first three factors do not change much. In general, given the same kind of vegetative cover, you expect areas with high-intensity precipitation, sandy or siltSilt refers to soil or rock particles of a certain very small size range (see grain size). On the Wentworth scale, silt particles fall between 0. 063 mm (4 62. 5 μm), larger than clay but smaller than a sand. In actuality, silt is chemically distinct fy soils, and steep slopes to be the most erosive. Soils with a lot of clayFor the town in the United States, see Clay, New York. Clay is a generic term for an aggregate of hydrous silicate particles less than 4 micrometers in diameter. It consists of small crystals of the minerals silica (SiO) and alumina (AlO). These elements, that receive less intense precipitation and are on gentle slopes tend to erode less.

The factor that is most subject to change is the amount and type of ground cover. When fires burn an area or when vegetation is removed as part of timber operations, building a house or a road, the susceptibility of the soil to erosion is greatly increased.

Roads are especially likely to cause increased rates of erosion because, in addition to removing ground cover, they can significantly change drainage patterns. A road that has a lot of rock and one that is "hydrologically invisible" (that gets the water off the road as quickly as possible, mimicking natural drainage patterns) has the best chance of not causing increased erosion.

One of the most serious and long-running water erosion problems on the planet is in ChinaThis article is on the geographic and cultural entity. For other meanings, see China (disambiguation). China ( Traditional Chinese: , Simplified Chinese: , Hanyu Pinyin: Zhongguo, Wade-Giles: Chung-kuo) is a country in continental East Asia with some oute, on the middle reaches of the Yellow River and the upper reaches of the Yangtze River. From the Yellow River, over 1.6 billion tons of sediment flow each year into the ocean. The sediment originates primarily from water erosion in the Loess PlateauThe Loess Plateau covers an area of some 640,000 km² in the upper and middle parts of China’s Yellow River. Loess is the name for the silty soil that has been deposited by wind storms on the plateau over the ages. Loess is a highly erosion-prone soil that region of northwest China.

1 Erosion processes

Gravity Erosion Mass-Wasting is the down-slope movement of rock and sediments, mainly due to the force of gravity. Mass-wasting is an important part of the erosional process, as it moves material from higher elevations to lower elevations where transporting agents like streams and glacierA glacier is a large, long-lasting river of ice that is formed on land and moves in response to gravity. Equivalently, it is a multi-year ice accretion in mountainous terrain. The glacier fringe is the area where the glacier has recently melted. There ares can then pick up the material and move it to even lower elevations. Mass-wasting processes are occurring continuously on all slopes; some mass-wasting processes act very slowly, others occur very suddenly, often with disastrous results. Any perceptible down-slope movement of rock or sediment is often referred to in general terms as a landslide. However, landslides can be classified in a much more detailed way that reflects the mechanisms responsible for the movement and the velocity at which the movement occurs.

Slumping happens on steep hillsides, occurring along distinct fracture zones, often within materials like clay, that, once released, may move quite rapidly downhill. They often will show a spoon-shaped depression within which the material has begun to slide downhill. In some cases the slump is caused by water beneath the slope weakening it. In many cases it is simply the result of poor engineering along highways where it is a regular occurrence.

Surface creep is the slow movement of soil and rock debris by gravity which is usually not perceptible except through extended observation. However, the term can also describe the rolling of dislodged soil particles 0.5 to 1.0 mm in diameter by wind along the soil surface.

Water erosion River erosion

Splash erosion is the detachment and airborne movement of small soil particles caused by the impact of raindrops on soils.

Wind or Aeolean erosion is the movement of rock and/or sediment by the wind. Windbreaks are often planted by farmers to reduce wind erosion. This includes the planting of trees, shrubs, or other vegetation, usually perpendicular or nearly so to the principal wind direction.

Ice erosion is erosion caused by ice. Glaciers can scrape and break up rock and then transport it, leaving moraines and drumlins in its wake. Ice wedging is the weathering process where water trapped in tiny rock cracks freezes and expands, causing the breakup of the rock. This can lead to gravity erosion on steep slopes. It is a common engineering problem wherever rock cliffs are alongside roads and morning thaws can drop hazardous rock pieces onto the road.

In materials science, erosion is the recession of surfaces by repeated localized mechanical trauma as, for example, by suspended abrasive particles within a moving fluid. Erosion can also occur from non-abrasive fluid mixtures. Cavitation is one example.

2 See also

3 Reference

World Bank 2001: China: Air, Land, and Water.

Geological processes Soil science

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