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{{Other uses|Erosion (disambiguation)}}{{pp|small=yes}}{{short description|Processes which remove soil and rock from one place on the Earth's crust, then transport it to another location where it is deposited}}File:Eroding rill in field in eastern Germany.jpg|thumb|right|An actively eroding rill on an intensively-farmed field in eastern Germany]]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 locationWEB,weblink Erosion, Encyclopædia Britannica, 2015-12-03, 2015-12-06,weblink" title="web.archive.org/web/20151221064037weblink">weblink 2015-12-21, live, (not to be confused with weathering which involves no movement). This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, animals, and humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolic) erosion, zoogenic erosion, and anthropogenic erosion.JOURNAL, Apollo, M., Andreychouk, V., Bhattarai, S.S., Short-Term Impacts of Livestock Grazing on Vegetation and Track Formation in a High Mountain Environment: A Case Study from the Himalayan Miyar Valley (India), Sustainability, 10, 4, 2018-03-24, 2071-1050, 10.3390/su10040951, 951, The particulate breakdown of rock or soil into clastic sediment is referred to as physical or mechanical erosion; this contrasts with chemical erosion, where soil or rock material is removed from an area by its dissolving into a solvent (typically water), followed by the flow away of that solution. Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.Natural rates of erosion are controlled by the action of geological weathering geomorphic drivers, such as rainfall;Cheraghi, M., S. Jomaa, G.C. Sander, and D.A. Barry (2016 ), Hysteretic sediment fluxes in rainfall-driven soil erosion: Particle size effects, Water Resour. Res., 52, {{doi|10.1002/2016WR019314}} file [weblink link]{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }} 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.g., by rain), storminess, wind speed, wave fetch, or atmospheric temperature (especially for some ice-related processes). 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.JOURNAL, Bernard, Hallet,weblink Glacial Abrasion and Sliding: Their Dependence on the Debris Concentration In Basal Ice, Annals of Glaciology, 1981, 2, 1, 23–28, 0260-3055, 10.3189/172756481794352487, 1981AnGla...2...23H, JOURNAL, Leonard S., Sklar,weblink A mechanistic model for river incision into bedrock by saltating bed load, Dietrich, William E., Water Resources Research, 2004, 40, 6, W06301, 0043-1397, 10.1029/2003WR002496, 2004WRR....40.6301S, 2016-06-18,weblink" title="web.archive.org/web/20161011172333weblink">weblink 2016-10-11, live, Processes of erosion that produce sediment or solutes from a place contrast with those of deposition, which control the arrival and emplacement of material at a new location.While erosion is a natural process, human activities have increased by 10-40 times the rate at which erosion is occurring globally.JOURNAL, Dotterweich, Markus, 2013-11-01, The history of human-induced soil erosion: Geomorphic legacies, early descriptions and research, and the development of soil conservation – A global synopsis, Geomorphology, 201, 1–34, 10.1016/j.geomorph.2013.07.021, 2013Geomo.201....1D, At well-known agriculture sites such as the Appalachian Mountains, intensive farming practices have caused erosion up to 100x the speed of the natural rate of erosion in the region.JOURNAL, Reusser, L., Bierman, P., Rood, D., Quantifying human impacts on rates of erosion and sediment transport at a landscape scale, Geology, 43, 2, 171–174, 10.1130/g36272.1, 2015Geo....43..171R, 2015, Excessive (or accelerated) erosion causes both "on-site" and "off-site" problems. 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, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses. Water and wind erosion are the two primary causes of land degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significant environmental problems worldwide.BOOK, Blanco-Canqui, Humberto, Rattan, Lal, Soil and water conservation, Principles of soil conservation and management, 1–20, 2008, Springer, Dordrecht, 978-1-4020-8709-7, {{rp|2}}BOOK, Toy, Terrence J., Foster, George R., Renard, Kenneth G., Soil erosion : processes, prediction, measurement, and control, 2002, Wiley, New York, 978-0-471-38369-7, {{rp|1}}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.BOOK, Julien, Pierre Y., Erosion and Sedimentation, Cambridge University Press, 2010, 978-0-521-53737-7, 1,weblink However, there are many prevention and remediation practices that can curtail or limit erosion of vulnerable soils.File:KharazaArch.jpg|thumb|A natural arch produced by the wind erosion of differentially weathered rock in Jebel Kharaz, JordanJordanFile:大连国家地质公园9-海蚀崖.JPG|thumb| A wave-like sea cliff produced by coastal erosion, in Jinshitan Coastal National Geopark, Dalian, Liaoning ProvinceLiaoning Province

Physical processes

Rainfall and surface runoff

File:Water and soil splashed by the impact of a single raindrop.jpg|thumb|right|Soil and water being splashed by the impact of a single raindropraindropRainfall, 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).{{rp|60–61}}BOOK, Zachar, Dušan, Classification of soil erosion, Soil Erosion, Vol. 10, Elsevier, 1982, 978-0-444-99725-8, 48,weblink In splash erosion, the impact of a falling raindrop creates a small crater in the soil,See Figure 1 in JOURNAL, Confined Shocks inside Isolated Liquid Volumes – A New Path of Erosion?, Physics of Fluids, 23, 10, 101702, 2011, 1109.3175, 2011PhFl...23j1702O, Obreschkow, D., Dorsaz, N., Kobel, P., De Bosset, A., Tinguely, M., Field, J., Farhat, M., 10.1063/1.3647583, ejecting soil particles.Cheraghi, M., S. Jomaa, G.C. Sander, and D.A. Barry (2016 ), Hysteretic sediment fluxes in rainfall-driven soil erosion: Particle size effects, Water Resour. Res., 52, {{doi|10.1002/2016WR019314}} The distance these soil particles travel can be as much as 0.6 m (two feet) vertically and 1.5 m (five feet) horizontally on level ground.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.BOOK, Food and Agriculture Organization, Types of erosion damage, Soil Erosion by Water: Some Measures for Its Control on Cultivated Lands, United Nations, 1965, 978-92-5-100474-6, 23–25,weblink Sheet erosion is the transport of loosened soil particles by overland flow.File:Rummu aherainemägi2.jpg|thumb|A spoil tip covered in rills and gullies due to erosion processes caused by rainfall: Rummu, EstoniaEstoniaRill 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.JOURNAL, Nearing, M.A., Norton, L.D., Bulgakov, D.A., Larionov, G.A., West, L.T., Dontsova, K.M., 1997, Hydraulics and erosion in eroding rills, Water Resources Research, 33, 4, 865–876, 10.1029/97wr00013, 1997WRR....33..865N, {{Anchor|gully erosion|ephemeral gully erosion}}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.BOOK, Boardman, John, Poesen, Jean, Soil Erosion in Europe, 2007, John Wiley & Sons, Chichester, 978-0-470-85911-7, BOOK, J. Poesen, L. Vandekerckhove, J. Nachtergaele, D. Oostwoud Wijdenes, G. Verstraeten, B. Can Wesemael, Gully erosion in dryland environments, 229–262, Bull, Louise J., Kirby, M.J., Dryland Rivers: Hydrology and Geomorphology of Semi-Arid Channels, John Wiley & Sons, 2002, 978-0-471-49123-1,weblink BOOK, Borah, Deva K., Watershed sediment yield, Garcia, Marcelo H., Sedimentation Engineering: Processes, Measurements, Modeling, and Practice, ASCE Publishing, 2008, 978-0-7844-0814-8, 828,weblink etal,

Rivers and streams

{{details|topic=water's erosive ability|Hydraulic action}}File: Dobbingstone Burn - geograph.org.uk - 1291882.jpg|thumb|Dobbingstone Burn, Scotland, showing two different types of erosion affecting the same place. Valley erosion is occurring due to the flow of the stream, and the boulders and stones (and much of the soil) that are lying on the stream's banks are glacial tillglacial tillValley 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.Ritter, Michael E. (2006) "Geologic Work of Streams" {{webarchive|url=https://web.archive.org/web/20120506040721weblink |date=2012-05-06 }} The Physical Environment: an Introduction to Physical Geography University of Wisconsin, {{OCLC|79006225}}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.BOOK,weblink Stream hydrology: an introduction for ecologists, Nancy D. Gordon, Erosion and Scour, 978-0-470-84357-4, 2004, Thermal erosion is the result of melting and weakening permafrost due to moving water.WEB,weblink Thermal Erosion, NSIDC Glossary, National Snow and Ice Data Center, 21 December 2009,weblink" title="web.archive.org/web/20101218124656weblink">weblink 2010-12-18, live, It can occur both along rivers and at the coast. 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.JOURNAL, 10.1002/esp.592, Fluvial thermal erosion investigations along a rapidly eroding river bank: application to the Lena River (central Siberia), 2003, Costard, F., Dupeyrat, L., Gautier, E., Carey-Gailhardis, E., Earth Surface Processes and Landforms, 28, 1349–1359, 2003ESPL...28.1349C, 12, Much of this erosion occurs as the weakened banks fail in large slumps. 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 {{convert|100|km|mi|abbr=off|adj=on}} segment of the Beaufort Sea shoreline averaged {{convert|5.6|m|ft|abbr=off}} per year from 1955 to 2002.JOURNAL, Jones, B.M., Hinkel, K.M., Arp, C.D., Eisner, W.R., 2008, Modern Erosion Rates and Loss of Coastal Features and Sites, Beaufort Sea Coastline, Alaska, Arctic, 61, 4, 361–372,weblink 10.14430/arctic44, dead,weblink" title="web.archive.org/web/20130517101602weblink">weblink 2013-05-17, 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.

Coastal erosion

{{See also|Beach evolution}}File:Wavecut platform southerndown pano.jpg|thumb|Wave cut platform caused by erosion of cliffs by the sea, at SoutherndownSoutherndownFile:Erosion of Boulder Clay in Filey Bay.JPG|thumb|Erosion of the boulder clay (of Pleistocene age) along cliffs of FileyFileyShoreline 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.File:Sea dune Erosion at Talace, Wales.webm|bawd|Dune Erosion at Talace, Wales.webm|thumb|Sea-dune Erosion at Talace beach, WalesWalesHydraulic 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.Geddes, Ian. "Lithosphere." Higher geography for cfe: physical and human environments, Hodder Education, 2015. Limestone cliffs are particularly vulnerable to this kind of erosion. Attrition is where particles/sea load carried by the waves are worn down as they hit each other and the cliffs. 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.Glynn, Peter W. "Bioerosion and coral-reef growth: a dynamic balance." Life and death of coral reefs (1997): 68-95.Sediment is transported along the coast in the direction of the prevailing current (longshore drift). When the upcurrent amount 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.Bell, Frederic Gladstone. "Marine action and control." Geological hazards: their assessment, avoidance, and mitigation, Taylor & Francis, 1999, pp. 302–306.

Chemical erosion

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. Anders Rapp pioneered the study of chemical erosion in his work about Kärkevagge published in 1960.JOURNAL, Dixon, John C., Thorn, Colin E., 2005, Chemical weathering and landscape development in mid-latitude alpine environments, Geomorphology (journal), Geomorphology, 67, 1–2, 127–145, 10.1016/j.geomorph.2004.07.009, 2005Geomo..67..127D,

Glaciers

File:MorainesLakeLouise.JPG|thumb|Glacial moraines above Lake Louise, in Alberta, CanadaAlberta, CanadaGlaciers erode predominantly by three different processes: abrasion/scouring, plucking, and ice thrusting. 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 100,000 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.JOURNAL, Harbor, Jonathan M., Hallet, Bernard, Raymond, Charles F., 1988-05-26, A numerical model of landform development by glacial erosion, Nature, en, 333, 6171, 347–349, 10.1038/333347a0, 1988Natur.333..347H, 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 1500 m.JOURNAL, Egholm, D. L., Nielsen, S. B., Pedersen, V.K., Lesemann, J.-E., Glacial effects limiting mountain height, Nature, 460, 7257, 884–887, 10.1038/nature08263, 19675651, 2009Natur.460..884E, 2009, The erosion caused by glaciers worldwide erodes mountains so effectively that the term glacial buzzsaw has become widely used, which describes the limiting effect of glaciers on the height of mountain ranges.JOURNAL, Thomson, Stuart N., Brandon, Mark T., Tomkin, Jonathan H., Reiners, Peter W., Vásquez, Cristián, Wilson, Nathaniel J., 2010, Glaciation as a destructive and constructive control on mountain building, Nature, 467, 7313, 313–317, 10.1038/nature09365, 20844534, 2010Natur.467..313T, As mountains grow higher, they generally allow for more glacial activity (especially in the accumulation zone above the glacial equilibrium line altitude),JOURNAL, Tomkin, J.H., Roe, G.H., 2007, Climate and tectonic controls on glaciated critical-taper orogens,weblink Earth Planet. Sci. Lett., 262, 3–4, 385–397, 10.1016/j.epsl.2007.07.040, 2007E&PSL.262..385T, 10.1.1.477.3927, 2017-10-24,weblink" title="web.archive.org/web/20170809121522weblink">weblink 2017-08-09, live, which causes increased rates of erosion of the mountain, decreasing mass faster than isostatic rebound can add to the mountain.Mitchell, S.G. & Montgomery, D.R. "Influence of a glacial buzzsaw on the height and morphology of the Cascade Range in central Washington State". Quat. Res. 65, 96–107 (2006) This provides a good example of a negative feedback loop. 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. Ice can not only erode mountains but also protect them from erosion. 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.JOURNAL, Gjermundsen, Endre F., Briner, Jason P., Akçar, Naki, Foros, Jørn, Kubik, Peter W., Salvigsen, Otto, Hormes, Anne, Minimal erosion of Arctic alpine topography during late Quaternary glaciation, Nature Geoscience, 8, 10, 789, 10.1038/ngeo2524, 2015NatGe...8..789G, 2015, 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.Harvey, A.M. "Local-Scale geomorphology – process systems and landforms." Introducing Geomorphology: A Guide to Landforms and Processes. Dunedin Academic Press, 2012, pp. 87–88. EBSCOhost.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.JOURNAL, Prasicek, Günther, Larsen, Isaac J., Montgomery, David R., 2015-08-14, Tectonic control on the persistence of glacially sculpted topography, Nature Communications, en, 6, 10.1038/ncomms9028, 2041-1723, 4557346, 26271245, 8028, 2015NatCo...6.8028P,

Floods

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.See, for example: BOOK, Alt, David, Glacial Lake Missoula & its Humongous Floods
year=2001url=https://books.google.com/books?id=s4y3c8fxeEwC,

Wind erosion

File:Im Salar de Uyuni.jpg|thumb|Árbol de Piedra, a rock formation in the Altiplano, BoliviaBoliviaWind 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.BOOK, Zheng, Xiaojing, Huang, Ning, Mechanics of Wind-Blown Sand Movements, Mechanics of Wind-Blown Sand Movements by Xiaojing Zheng. Berlin: Springer, Springer, 2009, 978-3-540-88253-4, 7–8,weblink 2009mwbs.book.....Z, BOOK, Cornelis, Wim S., Hydroclimatology of wind erosion in arid and semi-arid environments, D'Odorico, Paolo, Porporato, Amilcare, Dryland Ecohydrology, Springer, 2006, 978-1-4020-4261-4, 141,weblink 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. Saltation is responsible for the majority (50-70%) of wind erosion, followed by suspension (30-40%), and then surface creep (5-25%).BOOK, Blanco-Canqui, Humberto, Rattan, Lal, Wind erosion, Principles of soil conservation and management, 2008, Springer, Dordrecht, 978-1-4020-8709-7, 54–80, {{rp|57}}BOOK, Balba, A. Monem, Desertification: Wind erosion, Management of Problem Soils in Arid Ecosystems, CRC Press, 1995, 978-0-87371-811-0, 214,weblink 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 6100 times greater in drought years than in wet years.BOOK, Wiggs, Giles F.S., Geomorphological hazards in drylands, Thomas, David S.G., Arid Zone Geomorphology: Process, Form and Change in Drylands, John Wiley & Sons, 2011, 978-0-470-71076-0, 588,weblink

Mass movement

File:NegevWadi2009.JPG|thumb|A wadi in Makhtesh RamonMakhtesh RamonMass movement is the downward and outward movement of rock and sediments on a sloped surface, mainly due to the force of gravity.BOOK, Van Beek, Rens, Hillside processes: mass wasting, slope stability, and erosion, Norris, Joanne E., etal, Slope Stability and Erosion Control: Ecotechnological Solutions, Slope Stability and Erosion Control: Ecotechnological Solutions, Springer, 2008, 978-1-4020-6675-7,weblink 2008ssec.conf.....N, BOOK, Gray, Donald H., Sotir, Robbin B., Surficial erosion and mass movement, Biotechnical and Soil Bioengineering Slope Stabilization: A Practical Guide for Erosion Control, John Wiley & Sons, 1996, 978-0-471-04978-4, 20,weblink 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.BOOK, Nichols, Gary, Sedimentology and Stratigraphy, John Wiley & Sons, 2009, 978-1-4051-9379-5, {{rp|93}} It moves material from higher elevations to lower elevations where other eroding agents such as streams and glaciers can then pick up the material and move it to even lower elevations. 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.{{Citation needed|date=April 2012}}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. 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.BOOK, Sivashanmugam, P., Basics of Environmental Science and Engineering,weblink 2007, New India Publishing, 978-81-89422-28-8, 43–, 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 {{convert|0.5|to|1.0|mm|abbr=on|2}} in diameter by wind along the soil surface.WEB,weblink Britannica Library, library.eb.com, English, 2017-01-31,

Factors affecting erosion rates

Climate

{{see also|Climatic geomorphology}}The amount and intensity of precipitation is the main climatic factor governing soil erosion by water. The relationship is particularly strong if heavy rainfall occurs at times when, or in locations where, the soil's surface is not well protected by vegetation. This might be during periods when agricultural activities leave 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 and 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 rainfall), more wind, or more storms are expected to have more erosion.In some areas of the world (e.g. the mid-western USA), rainfall intensity is the primary determinant of erosivity (for a definition of erosivity check,BOOK, Encyclopedia of Natural Hazards, Zorn, Matija, Komac, Blaž, 2013, Springer Netherlands, 978-90-481-8699-0, Bobrowsky, Peter T., Encyclopedia of Earth Sciences Series, 289–290, en, 10.1007/978-1-4020-4399-4_121, ) with higher intensity rainfall generally resulting in more soil erosion by water. The size and velocity of rain drops is also an important factor. Larger and higher-velocity rain drops have greater kinetic energy, and thus their impact will displace soil particles by larger distances than smaller, slower-moving rain drops.BOOK, Blanco-Canqui, Humberto, Rattan, Lal, Water erosion, Principles of soil conservation and management, 2008, Springer, Dordrecht, 978-1-4020-8709-7, 21–53 [29–31], In other regions of the world (e.g. western Europe), runoff and erosion result from relatively low intensities of stratiform rainfall falling onto the previously saturated soil. In such situations, rainfall amount rather than intensity is the main factor determining the severity of soil erosion by water.In Taiwan, where typhoon frequency increased significantly in the 21st century, a strong link has been drawn between the increase in storm frequency with an increase in sediment load in rivers and reservoirs, highlighting the impacts climate change can have on erosion.JOURNAL, Montgomery, David R., Huang, Michelle Y.-F., Huang, Alice Y.-L., 2014-01-01, Regional soil erosion in response to land use and increased typhoon frequency and intensity, Taiwan,weblink Quaternary Research, 81, 1, 15–20, 10.1016/j.yqres.2013.10.005, 0033-5894, 2014QuRes..81...15M, 2017-02-23,weblink 2017-02-24, live,

Vegetative cover

{{See also|Vegetation and slope stability}}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 a more solid mass that is less susceptible to both waterJOURNAL, Gyssels, G., Poesen, J., Bochet, E., Li, Y., 2005-06-01, Impact of plant roots on the resistance of soils to erosion by water: a review, Progress in Physical Geography, en, 29, 2, 189–217, 10.1191/0309133305pp443ra, 0309-1333, and wind erosion. The removal of vegetation increases the rate of surface erosion.BOOK, Styczen, M.E., Morgan, R.P.C., Engineering properties of vegetation, Morgan, R.P.C., Rickson, R. Jane, Slope Stabilization and Erosion Control: A Bioengineering Approach, Taylor & Francis, 1995, 978-0-419-15630-7,weblink

Topography

The topography of the land determines the velocity at which surface runoff will flow, 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 steep slopes. Steeper terrain is also more prone to mudslides, landslides, and other forms of gravitational erosion processes.{{rp|28–30}}BOOK, Whisenant, Steve G., Terrestrial systems, Perrow Michael R., Davy, Anthony J., Handbook of Ecological Restoration: Principles of Restoration, Cambridge University Press, 2008, 978-0-521-04983-2, 89,weblink BOOK, Wainwright, John, Brazier, Richard E., Slope systems, Thomas, David S.G., Arid Zone Geomorphology: Process, Form and Change in Drylands, John Wiley & Sons, 2011, 978-0-470-71076-0,weblink

Tectonics

Tectonic processes control rates and distributions of erosion at the Earth's surface. If the tectonic action causes part of the Earth's surface (e.g., a mountain range) to be raised or lowered relative to surrounding areas, this must necessarily change the gradient of the land surface. Because erosion rates are almost always sensitive to the local slope (see above), this will change the rates of erosion in the uplifted area. Active tectonics also brings fresh, unweathered rock towards the surface, where it is exposed to the action of erosion.However, erosion can also affect tectonic processes. The removal by erosion of large amounts of rock from a particular region, and its deposition elsewhere, can result in a lightening of the load on the lower crust and mantle. Because tectonic processes are driven by gradients in the stress field developed in the crust, this unloading can in turn cause tectonic or isostatic uplift in the region.{{rp|99}}BOOK, Burbank, Douglas W., Anderson, Robert S., Tectonic and surface uplift rates, Tectonic Geomorphology, John Wiley & Sons, 2011, 978-1-4443-4504-9, 270–271,weblink In some cases, it has been hypothesised that these twin feedbacks can act to localize and enhance zones of very rapid exhumation of deep crustal rocks beneath places on the Earth's surface with extremely high erosion rates, for example, beneath the extremely steep terrain of Nanga Parbat in the western Himalayas. Such a place has been called a "tectonic aneurysm".Zeitler, P.K. et al. (2001), Erosion, Himalayan Geodynamics, and the Geomorphology of Metamorphism, GSA Today, 11, 4–9.

Development

Human land development, in forms including agricultural and urban development, is considered a significant factor in erosionJOURNAL, Chen, Jie, 2007-01-16, Rapid urbanization in China: A real challenge to soil protection and food security, CATENA, Influences of rapid urbanization and industrialization on soil resource and its quality in China, 69, 1, 1–15, 10.1016/j.catena.2006.04.019, and sediment transport. In Taiwan, increases in sediment load in the northern, central, and southern regions of the island can be tracked with the timeline of development for each region throughout the 20th century.

Erosion at various scales

Mountain ranges

{{see also|denudation|planation}}{{expand section|date=November 2015}}Mountain ranges are known to take many millions of years to erode to the degree they effectively cease to exist. Scholars Pitman and Golovchenko estimate that it takes probably more than 450 million years to erode a mountain mass similar to the Himalaya into an almost-flat peneplain if there are no major sea-level changes.JOURNAL, Pitman, W. C., Golovchenko, X., The effect of sea level changes on the morphology of mountain belts, Journal of Geophysical Research: Solid Earth, 96, B4, 1991, 6879–6891, 0148-0227, 10.1029/91JB00250, 1991JGR....96.6879P, Erosion of mountains massifs can create a pattern of equally high summits called summit accordance.BOOK, Chorley, Richard J., Beckinsale, Robert P., The History of the Study of Landforms, Volume Three, 1991, 2003, Taylor & Francis e-Library, Chapter Seven: American Polycyclic Geomorphology, 235–236, It has been argued that extension during post-orogenic collapse is a more effective mechanism of lowering the height of orogenic mountains than erosion.JOURNAL, Dewey, J.F., Ryan, P.D., Andersen, T.B., 1993, Orogenic uplift and collapse, crustal thickness, fabrics and metamorphic phase changes: the role of eclogites, Geological Society, London, Special Publications, 76, 1, 325–343, 10.1144/gsl.sp.1993.076.01.16, 1993GSLSP..76..325D, Examples of heavily eroded mountain ranges include the Timanides of Northern Russia. Erosion of this orogen has produced sediments that are now found in the East European Platform, including the Cambrian Sablya Formation near Lake Ladoga. Studies of these sediments indicate that it is likely that the erosion of the orogen began in the Cambrian and then intensified in the Ordovician.JOURNAL, Orlov, S.Yu., Kuznetsov, N.B., Miller, E.D., Soboleva, A.A., Udoratina, O.V., 2011, Age Constraints for the Pre-Uralide–Timanide Orogenic Event Inferred from the Study of Detrital Zircons,weblink Doklady Earth Sciences, 440, 1, 1216–1221, 10.1134/s1028334x11090078, 22 September 2015, 2011DokES.440.1216O,

Soils

{{further|soil erosion|pedogenesis}}If the rate of erosion is higher than the rate of soil formation the soils are being destroyed by erosion.ENCYCLOPEDIA, Lupia-Palmieri, Elvidio, Goudie, A.S., Andrew Goudie (geographer), Encyclopedia of Geomorphology, Erosion, 2004, 336, Where soil is not destroyed by erosion, erosion can in some cases prevent the formation of soil features that form slowly. Inceptisols are common soils that form in areas of fast erosion.BOOK, Alexander, Earl B., 2014, Soils in natural landscapes, CRC Press, 108, 978-1-4665-9436-4, While erosion of soils is a natural process, human activities have increased by 10-40 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 (on natural landscapes) ecological collapse, both because of loss of the nutrient-rich upper soil layers. In some cases, the eventual end result is desertification. Off-site effects include sedimentation of waterways and eutrophication of water bodies, as well as sediment-related damage to roads and houses. Water and wind erosion are the two primary causes of land degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significant environmental problems.BOOK, Blanco, Humberto, Lal, Rattan, Soil and water conservation, Principles of Soil Conservation and Management, Springer, 2010, 978-90-481-8529-0, 2,weblink

Consequences of human-made soil erosion

See also

{{Div col}}
  • {{annotated link|Badlands}}
  • {{annotated link|Biorhexistasy}}
  • {{annotated link|Bridge scour}}
  • {{annotated link|Cellular confinement}}
  • {{annotated link|Coastal sediment supply}}
  • {{annotated link|Food security}}
  • {{annotated link|Geomorphology}}
  • {{annotated link|Groundwater sapping}}
  • {{annotated link|Highly erodible land}}
  • {{annotated link|Ice jacking}}
  • {{annotated link|Lessivage}}
  • {{annotated link|Lisasion}}
  • {{annotated link|Raised beach|Marine terrace}}
  • {{annotated link|Riparian zone}}
  • {{annotated link|River anticlines}}
  • {{annotated link|Sediment transport}}
  • {{annotated link|Sinkhole}}
  • {{annotated link|Soil erosion}}
  • {{annotated link|Space weathering}}
  • {{annotated link|Sphericity}}
  • {{annotated link|TERON (Tillage erosion)}}
  • {{annotated link|Vetiver System}}
  • {{annotated link|Weathering}}
  • {{annotated link|Erodability}}
{{Div col end}}

References

{{reflist}}

Further reading

  • BOOK, Boardman, John, Poesen, Jean, Soil Erosion in Europe, 2007, John Wiley & Sons, Chichester, 978-0-470-85911-7,
  • BOOK, Montgomery, David, Dirt: The Erosion of Civilizations, University of California Press, 2008, 1st, 978-0-520-25806-8,weblink
  • JOURNAL, Montgomery, D.R., Soil erosion and agricultural sustainability, Proceedings of the National Academy of Sciences, 8 August 2007, 104, 33, 13268–13272, 10.1073/pnas.0611508104, 17686990, 2007PNAS..10413268M, 1948917,
  • BOOK, Vanoni, Vito A., The nature of sedimentation problems, Sedimentation Engineering, ASCE Publications, 978-0-7844-0823-0,weblink 1975,
  • BOOK,weblink Mainguet, Monique, Dumay, Frédéric, April 2011, Fighting wind erosion. One aspect of the combat against desertification, Les dossiers thématiques du CSFD, 3, CSFD/Agropolis International, 7 October 2015,

External links

{{Sister project links|Erosion}} {{River morphology}}{{Authority control}}


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