What is soil erosion wikipedia

what is soil erosion wikipedia

Soil erosion is the displacement of the upper layer of soil; it is a form of soil alldatingloveen.com natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, animals, and alldatingloveen.com accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolean) erosion, zoogenic. In earth science, erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location. Erosion is distinct from weathering which involves no movement. Removal of rock or soil as clastic sediment is referred to as physical or mechanical erosion; this contrasts.

Soil erosion is the displacement of the upper layer of soil ; it is a form of soil wikiedia. This natural process is caused by the dynamic activity of erosive agents, that is, waterice glacierssnowair windplantsanimalswikpedia humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosionsnow erosion, wind aeolean erosionzoogenic erosion and anthropogenic erosion such as tillage erosion.

The loss of soil from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks. Soil erosion could also cause sinkholes. Human activities have increased by 10—50 times the rate at which erosion is occurring globally. Excessive or accelerated erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases in agricultural productivity and wikipevia natural landscapes ecological collapseboth because of loss of the nutrient-rich upper soil layers.

In some cases, the eventual end result wiiipedia desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as how to get the formula in excel as sediment-related damage to roads and houses. Intensive agriculturedeforestationroadsanthropogenic climate change and urban sprawl are amongst the most significant human activities in regard how to spell the letters of the english alphabet their effect on stimulating erosion.

Rainfalland the surface runoff which may result from rainfall, produces four what is soil erosion wikipedia types of soil erosion: splash erosionsheet erosionrill erosionand gully erosion. Splash erosion is generally seen as the first and least severe stage in i soil erosion process, which is followed soio sheet erosion, then rill erosion and finally gully erosion the most severe of the four. In splash erosionthe impact of a falling raindrop creates a small crater in the soil, [7] ejecting soil particles.

If the soil is saturatedor if the rainfall rate is greater than the rate at which water can infiltrate into the soil, surface wiipedia occurs. If the runoff has sufficient flow energyit will transport loosened soil particles sediment down the slope. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes.

Generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimeters about an inch wgat less and along-channel slopes may be quite steep. This means that rills exhibit hydraulic physics very different from water flowing erosioh the deeper wider channels of streams and rivers.

Gully erosion occurs when runoff water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow, removing soil to a zoil depth.

Valley or stream erosion occurs with continued water flow along a linear feature. The erosion is both downwarddeepening wikpiedia valley, and headwardextending the valley into the hillside, creating head cuts and steep banks. In the earliest stage of stream erosion, the erosive what is soil erosion wikipedia is dominantly vertical, the valleys have a typical V cross-section and the stream gradient is relatively steep.

When some base level is reached, the erosive activity wat to lateral erosion, which widens the valley floor and creates a narrow floodplain.

The stream gradient becomes nearly flat, and lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion, by far the most erosion occurs during times of flood, when more and faster-moving water is available to carry a larger sediment load.

In such processes, it is not the water wikipdeia that erodes: suspended abrasive particles, pebbles and boulders can also act erosively as eroion traverse erosikn surfacein a process known as traction. Bank erosion is the wearing away of the banks of a stream or river. This is distinguished from changes on the bed of the watercourse, which is referred to as scour.

Erosion and changes in the form of river banks may be measured by inserting metal rods into the bank and marking the position of the bank surface along the rods at different times.

Thermal erosion is the result of melting and weakening permafrost ls to moving water. Rapid river channel migration observed in the Lena River of Siberia is due to thermal erosion wikipexia, as these portions of the banks are composed of permafrost-cemented non-cohesive materials.

Thermal erosion also affects the Arctic coast, where wave action and near-shore temperatures combine to undercut permafrost bluffs along the shoreline and cause them to fail.

Annual erosion hwat along a kilometre mile what is soil erosion wikipedia of the Beaufort Sea shoreline averaged 5. At extremely high flows, kolksor vortices are formed by large volumes of rapidly rushing water. Kolks cause extreme local erosion, plucking bedrock and creating pothole-type geographical wikiprdia called Rock-cut basins. Examples can be seen in the flood regions result from glacial Lake Missoulawhich created the channeled scablands in the Columbia Basin region of eastern Washington.

Wind erosion is a major geomorphological force, wikipeddia in arid and semi-arid regions. It is iz a major source of land degradation, evaporation, desertification, harmful airborne dust, and crop damage—especially after being increased far above natural rates by human activities such as deforestationurbanizationand agriculture.

Wind erosion is of two primary varieties: deflationwhere the wind picks up and wokipedia away loose particles; and abrasionwhere surfaces are worn down as they are struck by airborne particles carried by wind. Deflation is divided into three categories: 1 surface when you first start birth control what to expectwhere larger, heavier particles slide or roll along the ground; 2 saltationwhere particles are lifted a short height shat the air, and bounce and saltate across the surface of the soil; and 3 wiipediawhere very small and light particles are lifted into the air by the wind, and are often carried for long distances.

Wind erosion is much more severe in arid areas and during times of ersion. For example, in the Great Plainsit is estimated that soil loss due to wind erosion can be as much as times greater in drought years than in wet years.

Mass movement is the downward and outward movement of rock and sediments on a sloped surface, mainly due to the force of gravity. Mass movement is an important what is soil erosion wikipedia of the erosional process, and is often the first stage in the breakdown and transport of weathered materials in mountainous areas.

Mass-movement processes are always occurring continuously on all slopes; some mass-movement processes act very slowly; others wioipedia 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. One of the visible topographical manifestations of a very slow form of such activity is a scree slope. Slumping happens on steep hillsides, occurring along distinct fracture zones, often within materials like clay that, once released, may move quite rapidly downhill. They will often show a spoon-shaped isostatic depressionin which the what kind of wine goes with grilled salmon has begun to slide downhill.

In some cases, the slump is caused by water beneath the slope weakening it. In many wiiipedia it is woil the result of poor ahat 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. Tillage erosion is a form of soil erosion occurring in cultivated fields due to the movement of soil by tillage. The amount and intensity of precipitation is the main climatic factor governing soil erosion by eroson. The relationship is particularly strong if heavy rainfall occurs at times when, or in locations where, the soil's surface is not well os by vegetation.

This might be during periods when agricultural activities wikipedla the soil bare, or in semi-arid regions where vegetation is naturally sparse. Wind erosion requires strong winds, particularly during times of drought when vegetation is sparse wikipediia soil is dry and so is more erodible. Other climatic factors such as average temperature and temperature range may also affect erosion, via their effects on vegetation and soil properties.

In general, given similar vegetation and ecosystems, areas with more precipitation especially high-intensity rainfallmore wind, or more storms are expected to have more erosion.

In some areas of the world e. The size and velocity of rain drops is also wjat important factor. Larger and higher-velocity rain drops have greater kinetic energyand thus their impact will displace soil particles by larger distances than smaller, slower-moving rain drops. In other regions of the world e. In such situations, rainfall amount rather than intensity is the main factor determining the severity of soil erosion by water.

The composition, moisture, and compaction of soil are all major factors in determining the erosivity of rainfall. Sediments containing more clay tend to be more resistant to erosion than those with sand or silt, because the clay helps bind soil particles together.

Wet, saturated soils will not be able to absorb as much rain water, leading to higher levels of wikipedoa runoff and thus higher erosivity for a given volume of rainfall.

More compacted soils will have a larger amount of surface runoff than less compacted soils. Vegetation acts as an interface between the atmosphere and the soil. It increases the permeability of the soil to rainwater, thus decreasing runoff.

It shelters the soil from winds, which results in decreased wind erosion, as well as advantageous changes in microclimate. The roots of the plants bind the soil together, and interweave with other roots, forming erlsion more solid mass that is less susceptible to both water and wind erosion. What can i claim on my tax return 2013 removal of vegetation increases the rate of surface erosion.

The topography of the land determines the velocity at which surface runoff will soi, which in turn determines the erosivity of the runoff. Longer, steeper slopes especially those without adequate vegetative cover are more susceptible to very high rates of erosion during heavy rains than shorter, less sewing machine how to buy slopes.

Steeper terrain is also more prone to mudslides, landslides, and other forms of gravitational erosion processes. Unsustainable agricultural practices increase rates of erosion by one to two orders of magnitude over the natural rate and far exceed replacement by soil production.

The problem has been exacerbated in modern times, due wikopedia mechanized agricultural equipment that allows for deep plowingwhich severely increases the amount of soil that is available for transport by water erosion. Others include mono-croppingfarming on steep slopes, pesticide and chemical fertilizer usage which kill organisms that bind soil togetherrow-cropping, and the use of surface irrigation.

Loss of total phosphorusfor instance, in the finer eroded fraction is greater relative to erosiom whole soil. Exacerbating this is the fact that most of the trees are generally whzt from agricultural fields, allowing winds to have wikipedla, open runs to travel over at higher speeds.

In an undisturbed forestthe mineral soil is protected eroson a layer of leaf litter and an humus that cover the forest ks. These two layers form a protective mat over the soil that absorbs the impact of rain drops. They are porous and highly permeable to rainfall, and allow rainwater to slow percolate into the soil below, instead of flowing over the surface as runoff. The terminal velocity of rain drops is reached in about 8 metres 26 feet.

Because forest canopies are usually higher than this, rain drops can often regain terminal velocity even after striking the canopy. However, the intact forest floor, with its layers of leaf litter and organic matter, is still able to absorb the impact of the rainfall. Deforestation causes increased erosion rates due to exposure of mineral soil by removing the humus and litter layers from the soil surface, removing the vegetative cover that binds soil together, and causing heavy soil compaction from logging equipment.

Once trees have been removed by fire or logging, infiltration rates become high and erosion low to the degree the forest floor remains intact.

Severe fires can lead to significant further erosion if followed by heavy rainfall. Globally one of the how to install a snap on leather contributors to erosive soil loss in the year is the slash and burn treatment of tropical forests. In a number of regions of the earth, entire sectors of a country have been rendered unproductive.

For example, on the Madagascar high central plateaucomprising approximately ten percent of that country's land area, virtually the entire landscape is sterile of vegetationwith gully erosive furrows typically in excess of 50 metres ft deep and 1 kilometre 0. Soi cultivation is a farming system which sometimes incorporates the slash and burn method in some regions of the world.

This degrades the soil and causes the soil to become less and less fertile.

Navigation menu

Soil erosion is the washing or blowing away (by water or wind) of the top layer of soil (dirt). This is a serious problem for alldatingloveen.com the soil has eroded, the crops that make food will not grow very well.. Soil erosion was a big problem in the Midwestern United States in the s dust bowl.. Erosion also leaves large sinkholes in the ground, which can weaken buildings and even cause them.

In earth science , erosion is the action of surface processes such as water flow or wind that removes soil , rock , or dissolved material from one location on the Earth's crust , and then transports it to another location. Erosion is distinct from weathering which involves no movement. Agents of erosion include rainfall ; [4] bedrock wear in rivers ; coastal erosion by the sea and waves ; glacial plucking, abrasion , and scour; areal flooding; wind abrasion; groundwater processes; and mass movement processes in steep landscapes like landslides and debris flows.

The rates at which such processes act control how fast a surface is eroded. Typically, physical erosion proceeds fastest on steeply sloping surfaces, and rates may also be sensitive to some climatically-controlled properties including amounts of water supplied e.

Feedbacks are also possible between rates of erosion and the amount of eroded material that is already carried by, for example, a river or glacier. While erosion is a natural process, human activities have increased by times the rate at which erosion is occurring globally. On-site impacts include decreases in agricultural productivity and on natural landscapes ecological collapse , both because of loss of the nutrient-rich upper soil layers.

In some cases, this leads to desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses. Intensive agriculture , deforestation , roads , anthropogenic climate change and urban sprawl are amongst the most significant human activities in regard to their effect on stimulating erosion.

Rainfall , and the surface runoff which may result from rainfall, produces four main types of soil erosion : splash erosion , sheet erosion , rill erosion , and gully erosion. Splash erosion is generally seen as the first and least severe stage in the soil erosion process, which is followed by sheet erosion, then rill erosion and finally gully erosion the most severe of the four.

In splash erosion , the impact of a falling raindrop creates a small crater in the soil, [14] ejecting soil particles. If the soil is saturated , or if the rainfall rate is greater than the rate at which water can infiltrate into the soil, surface runoff occurs.

If the runoff has sufficient flow energy , it will transport loosened soil particles sediment down the slope. Rill erosion refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery systems for erosion on hillslopes. Generally, where water erosion rates on disturbed upland areas are greatest, rills are active. Flow depths in rills are typically of the order of a few centimetres about an inch or less and along-channel slopes may be quite steep.

This means that rills exhibit hydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers. Gully erosion occurs when runoff water accumulates and rapidly flows in narrow channels during or immediately after heavy rains or melting snow, removing soil to a considerable depth. Extreme gully erosion can progress to formation of badlands. These form under conditions of high relief on easily eroded bedrock in climates favorable to erosion.

Conditions or disturbances that limit the growth of protective vegetation rhexistasy are a key element of badland formation. Valley or stream erosion occurs with continued water flow along a linear feature. The erosion is both downward , deepening the valley , and headward , extending the valley into the hillside, creating head cuts and steep banks.

In the earliest stage of stream erosion, the erosive activity is dominantly vertical, the valleys have a typical V cross-section and the stream gradient is relatively steep. When some base level is reached, the erosive activity switches to lateral erosion, which widens the valley floor and creates a narrow floodplain.

The stream gradient becomes nearly flat, and lateral deposition of sediments becomes important as the stream meanders across the valley floor. In all stages of stream erosion, by far the most erosion occurs during times of flood when more and faster-moving water is available to carry a larger sediment load.

In such processes, it is not the water alone that erodes: suspended abrasive particles, pebbles , and boulders can also act erosively as they traverse a surface, in a process known as traction.

Bank erosion is the wearing away of the banks of a stream or river. This is distinguished from changes on the bed of the watercourse, which is referred to as scour. Erosion and changes in the form of river banks may be measured by inserting metal rods into the bank and marking the position of the bank surface along the rods at different times.

Thermal erosion is the result of melting and weakening permafrost due to moving water. Rapid river channel migration observed in the Lena River of Siberia is due to thermal erosion, as these portions of the banks are composed of permafrost-cemented non-cohesive materials.

Thermal erosion also affects the Arctic coast , where wave action and near-shore temperatures combine to undercut permafrost bluffs along the shoreline and cause them to fail.

Annual erosion rates along a kilometre mile segment of the Beaufort Sea shoreline averaged 5. Most river erosion happens nearer to the mouth of a river.

On a river bend, the longest least sharp side has slower moving water. Here deposits build up. On the narrowest sharpest side of the bend, there is faster moving water so this side tends to erode away mostly.

Rapid erosion by a large river can remove enough sediments to produce a river anticline , [26] as isostatic rebound raises rock beds unburdened by erosion of overlying beds. Shoreline erosion, which occurs on both exposed and sheltered coasts, primarily occurs through the action of currents and waves but sea level tidal change can also play a role.

Hydraulic action takes place when the air in a joint is suddenly compressed by a wave closing the entrance of the joint. This then cracks it. Wave pounding is when the sheer energy of the wave hitting the cliff or rock breaks pieces off. Abrasion or corrasion is caused by waves launching sea load at the cliff. It is the most effective and rapid form of shoreline erosion not to be confused with corrosion. Corrosion is the dissolving of rock by carbonic acid in sea water.

This then makes the material easier to wash away. The material ends up as shingle and sand. Another significant source of erosion, particularly on carbonate coastlines, is boring, scraping and grinding of organisms, a process termed bioerosion.

Sediment is transported along the coast in the direction of the prevailing current longshore drift. When the upcurrent supply of sediment is less than the amount being carried away, erosion occurs. When the upcurrent amount of sediment is greater, sand or gravel banks will tend to form as a result of deposition.

These banks may slowly migrate along the coast in the direction of the longshore drift, alternately protecting and exposing parts of the coastline.

Where there is a bend in the coastline, quite often a buildup of eroded material occurs forming a long narrow bank a spit. Armoured beaches and submerged offshore sandbanks may also protect parts of a coastline from erosion. Over the years, as the shoals gradually shift, the erosion may be redirected to attack different parts of the shore.

Erosion of a coastal surface, followed by a fall in sea level, can produce a distinctive landform called a raised beach. Chemical erosion is the loss of matter in a landscape in the form of solutes. Chemical erosion is usually calculated from the solutes found in streams.

Formation of sinkholes and other features of karst topography is an example of extreme chemical erosion. In an abrasion process, debris in the basal ice scrapes along the bed, polishing and gouging the underlying rocks, similar to sandpaper on wood. Scientists have shown that, in addition to the role of temperature played in valley-deepening, other glaciological processes, such as erosion also control cross-valley variations. In a homogeneous bedrock erosion pattern, curved channel cross-section beneath the ice is created.

Though the glacier continues to incise vertically, the shape of the channel beneath the ice eventually remain constant, reaching a U-shaped parabolic steady-state shape as we now see in glaciated valleys. Scientists also provide a numerical estimate of the time required for the ultimate formation of a steady-shaped U-shaped valley —approximately , years.

In a weak bedrock containing material more erodible than the surrounding rocks erosion pattern, on the contrary, the amount of over deepening is limited because ice velocities and erosion rates are reduced. Glaciers can also cause pieces of bedrock to crack off in the process of plucking. In ice thrusting, the glacier freezes to its bed, then as it surges forward, it moves large sheets of frozen sediment at the base along with the glacier.

This method produced some of the many thousands of lake basins that dot the edge of the Canadian Shield. Differences in the height of mountain ranges are not only being the result tectonic forces, such as rock uplift, but also local climate variations. Scientists use global analysis of topography to show that glacial erosion controls the maximum height of mountains, as the relief between mountain peaks and the snow line are generally confined to altitudes less than m. Ongoing research is showing that while glaciers tend to decrease mountain size, in some areas, glaciers can actually reduce the rate of erosion, acting as a glacial armor.

Depending on glacier regime, even steep alpine lands can be preserved through time with the help of ice. Scientists have proved this theory by sampling eight summits of northwestern Svalbard using Be10 and Al26, showing that northwestern Svalbard transformed from a glacier-erosion state under relatively mild glacial maxima temperature, to a glacier-armor state occupied by cold-based, protective ice during much colder glacial maxima temperatures as the Quaternary ice age progressed.

These processes, combined with erosion and transport by the water network beneath the glacier, leave behind glacial landforms such as moraines , drumlins , ground moraine till , kames, kame deltas, moulins, and glacial erratics in their wake, typically at the terminus or during glacier retreat.

The best-developed glacial valley morphology appears to be restricted to landscapes with low rock uplift rates less than or equal to 2 mm per year and high relief, leading to long-turnover times.

Where rock uplift rates exceed 2 mm per year, glacial valley morphology has generally been significantly modified in postglacial time. Interplay of glacial erosion and tectonic forcing governs the morphologic impact of glaciations on active orogens, by both influencing their height, and by altering the patterns of erosion during subsequent glacial periods via a link between rock uplift and valley cross-sectional shape.

At extremely high flows, kolks , or vortices are formed by large volumes of rapidly rushing water. Kolks cause extreme local erosion, plucking bedrock and creating pothole-type geographical features called rock-cut basins. Examples can be seen in the flood regions result from glacial Lake Missoula , which created the channeled scablands in the Columbia Basin region of eastern Washington.

Wind erosion is a major geomorphological force, especially in arid and semi-arid regions. It is also a major source of land degradation, evaporation, desertification, harmful airborne dust, and crop damage—especially after being increased far above natural rates by human activities such as deforestation , urbanization , and agriculture. Wind erosion is of two primary varieties: deflation , where the wind picks up and carries away loose particles; and abrasion , where surfaces are worn down as they are struck by airborne particles carried by wind.

Deflation is divided into three categories: 1 surface creep , where larger, heavier particles slide or roll along the ground; 2 saltation , where particles are lifted a short height into the air, and bounce and saltate across the surface of the soil; and 3 suspension , where very small and light particles are lifted into the air by the wind, and are often carried for long distances.

Wind erosion is much more severe in arid areas and during times of drought. For example, in the Great Plains , it is estimated that soil loss due to wind erosion can be as much as times greater in drought years than in wet years. Mass movement is the downward and outward movement of rock and sediments on a sloped surface, mainly due to the force of gravity. Mass movement is an important part of the erosional process and is often the first stage in the breakdown and transport of weathered materials in mountainous areas.

Mass-movement processes are always occurring continuously on all slopes; some mass-movement 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.

One of the visible topographical manifestations of a very slow form of such activity is a scree slope. Slumping happens on steep hillsides, occurring along distinct fracture zones, often within materials like clay that, once released, may move quite rapidly downhill.

They will often show a spoon-shaped isostatic depression , in which the material has begun to slide downhill.



More articles in this category:
<- What happened to free realms 2014 - What does the bible say about homosexuality catholic->

5 thoughts on “What is soil erosion wikipedia

Add a comment

Your email will not be published. Required fields are marked *

Back to top