Comparing River and Glacial Erosion

Erosion is a broadly defined group of processes involving the movement of soil and rock. Erosion is

caused by wind action, river and stream processes, marine processes (sea waves), and glacial processes. The

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.

Weathering is the physical and chemical changes in rocks and minerals at or near the surface of Earth. So,

in a general sense, weathering occurs everywhere and begins to show the effects of physical wear and tear on

objects. Moving water is the most important natural agent of erosion. One type of erosion which is caused by sea

waves 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 dry 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.

In addition to the erosive power of saltwater waves on the shore, there is the force exerted by running

water in creeks, streams, and rivers. As the river moves, pushing along sediment and other materials eroded from

the streambed or riverbed, it carves out deep gaps in the bedrock beneath. These moving bodies of water

continually reshape the land, carrying soil and debris down slope, or from the source of the river to its mouth or

delta. A delta is a region of sediment formed when a river enters a larger body of water, at which point the

reduction in velocity on the part of the river current leads to the widespread deposition (depositing) of sediment.

Ice, of course, is simply another form of water, but since it is solid, its physical properties are quite

different. A glacier is a large, typically moving mass of ice either on or adjacent to a land surface. It does not

flow in the same way that water does; rather, it is moved by gravity, as a consequence of its extraordinary weight.

Under certain conditions, a glacier may have a layer of melted water surrounding it, which greatly enhances its

mobility. Regardless of whether it has this lubricant, however, a glacier steadily moves forward, carrying pieces

of rock, soil, and vegetation with it. These great rivers of ice gouge out pieces of bedrock from mountain slopes,

fashioning deep valleys. Ice along the bottom of the glacier pulls away rocks and soil, which assist it in wearing

away bedrock.

Speed, of course, is a relative term when speaking about processes involved in the shaping of the planet. A

fast glacier, one whose movement is assisted by a wet and warm maritime climate, moves at a faster per year. By

contrast, in the dry, exceptionally cold, inland climate of Antarctica, the glaciers moves at a slower rate per year.

Freezing water

River weathering

Glacial erosion

Work Cited

"Coastal and Nearshore Erosion." United States Geological Survey (USGS) (Web site).

<http://walrus.wr.usgs.gov/hazards/erosion.html>.

Protecting Your Property from Erosion (Web site). <http://www.abag.ca.gov/bayarea/enviro/erosion/erosion.html>.

Weathering and Erosion (Web site). <http://vishnu.glg.nau.edu/people/jhw/GLG101/Weathering.html>.

Wind Erosion Research Unit. United States Department of Agriculture/Kansas State University (Web site). <http://www.weru.ksu.edu/>.

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