An actively erodingrill on anintensively-farmed field ineasternGermany. This phenomenon is aggravated by poor agricultural practices because whenploughing, the furrows were traced in the direction of the slope rather than that of the terraincontour lines.
Erosion is the action of surface processes (such aswater flow orwind) that removessoil,rock, or dissolved material from one location on theEarth's crust and thentransports it to another location where it isdeposited. Erosion is distinct fromweathering which involves no movement.[1][2] Removal of rock or soil asclasticsediment is referred to asphysical ormechanical erosion; this contrasts withchemical erosion, where soil or rock material is removed from an area bydissolution.[3] Eroded sediment or solutes may be transported just a few millimetres, or for thousands of kilometres.
Agents of erosion includerainfall;[4]bedrock wear inrivers;coastal erosion by the sea andwaves;glacialplucking,abrasion, and scour; areal flooding;wind abrasion;groundwater processes; andmass movement processes in steeplandscapes likelandslides anddebris flows. The rates at which such processes act control how fast a surface is eroded. Typically, physical erosion proceeds the 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, wavefetch, oratmospheric 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.[5][6] The transport of eroded materials from their original location is followed by deposition, which is arrival and emplacement of material at a new location.[1]
While erosion is a natural process, human activities have increased by 10–40 times the rate at whichsoil erosion is occurring globally.[7] At agriculture sites in theAppalachian Mountains, intensive farming practices have caused erosion at up to 100 times the natural rate of erosion in the region.[8] Excessive (or accelerated) erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases inagricultural productivity and (onnatural landscapes)ecological collapse, both because of loss of the nutrient-rich uppersoil layers. In some cases, this leads todesertification. Off-site effects includesedimentation of waterways andeutrophication ofwater bodies, as well as sediment-related damage to roads and houses. Water and wind erosion are the two primary causes ofland degradation; combined, they are responsible for about 84% of the global extent of degraded land, making excessive erosion one of the most significantenvironmental problems worldwide.[9]: 2 [10]: 1 [11]
Rainfall, and thesurface runoff which may result from rainfall, produces four main types ofsoil erosion:splash erosion,sheet erosion,rill erosion, andgully 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).[10]: 60–61 [13]
Insplash erosion, theimpact of a falling raindrop creates a small crater in thesoil,[14] ejecting soil particles.[4] The distance these soil particles travel can be as much as 0.6 m (2.0 ft) vertically and 1.5 m (4.9 ft) horizontally on level ground.
Aspoil tip covered in rills and gullies due to erosion processes caused by rainfall:Rummu,Estonia
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 exhibithydraulic physics very different from water flowing through the deeper, wider channels of streams and rivers.[16]
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.[17][18][19] A gully is distinguished from a rill based on a critical cross-sectional area of at least one square foot, i.e. the size of a channel that can no longer be erased via normal tillage operations.[20]
Extreme gully erosion can progress to formation ofbadlands. These form under conditions of high relief oneasily 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.[21]
DobbingstoneBurn, 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 areglacial till that was left behind as ice age glaciers flowed over the terrain.Layers ofchalk exposed by a river eroding through themGreen land erosion
Valley orstream erosion occurs with continued water flow along alinear feature. The erosion is bothdownward, deepening thevalley, andheadward, extending the valley into the hillside, creatinghead cuts and steep banks. In the earliest stage of stream erosion, the erosive activity is dominantly vertical, the valleys have a typical V-shaped cross-section and the stream gradient is relatively steep. When somebase 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 streammeanders 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, andboulders can also act erosively as they traverse a surface, in a process known astraction.[22]
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 asscour. Erosion andchanges 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.[23]
Thermal erosion is the result of melting and weakeningpermafrost due to moving water.[24] It can occur both along rivers and at the coast. Rapidriver channel migration observed in theLena River of Siberia is due to thermal erosion, as these portions of the banks are composed of permafrost-cemented non-cohesive materials.[25] Much of this erosion occurs as the weakened banks fail in large slumps. Thermal erosion also affects theArctic 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 100-kilometre (62-mile) segment of theBeaufort Sea shoreline averaged 5.6 metres (18 feet) per year from 1955 to 2002.[26]
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 ariver anticline,[27] asisostatic 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 andwaves 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 orcorrasion 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 withcorrosion).Corrosion is the dissolving of rock bycarbonic acid in sea water.[28]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 asshingle and sand. Another significant source of erosion, particularly on carbonate coastlines, is boring, scraping and grinding of organisms, a process termedbioerosion.[29]
Sediment is transported along the coast in the direction of the prevailing current (longshore drift). When the upcurrentsupply 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 ofdeposition. 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 (aspit).Armoured beaches and submerged offshoresandbanks 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.[30]
Erosion of a coastal surface, followed by a fall in sea level, can produce a distinctive landform called araised beach.[31]
Chemical erosion is the loss of matter in a landscape in the form ofsolutes. Chemical erosion is usually calculated from the solutes found in streams.Anders Rapp pioneered the study of chemical erosion in his work aboutKärkevagge published in 1960.[32]
Formation ofsinkholes and other features of karst topography is an example of extreme chemical erosion.[33]
Glaciers 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 inglaciated valleys. Scientists also provide a numerical estimate of the time required for the ultimate formation of a steady-shapedU-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.[35]
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 theCanadian 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.[36] The erosion caused by glaciers worldwide erodes mountains so effectively that the termglacial buzzsaw has become widely used, which describes the limiting effect of glaciers on the height of mountain ranges.[37] As mountains grow higher, they generally allow for more glacial activity (especially in theaccumulation zone above the glacial equilibrium line altitude),[38] which causes increased rates of erosion of the mountain, decreasing mass faster thanisostatic rebound can add to the mountain.[39] This provides a good example of anegative 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 aglacial armor.[37] 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.[40]
The best-developed glacial valley morphology appears to be restricted to landscapes with low rock uplift rates (less than or equal to 2mm per year) and high relief, leading to long-turnover times. Where rock uplift rates exceed 2mm 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.[42]
Floods
The mouth of theRiver Seaton inCornwall after heavy rainfall caused flooding in the area and cause a significant amount of the beach to erode; leaving behind a tall sand bank in its place
At extremely high flows,kolks, orvortices are formed by large volumes of rapidly rushing water. Kolks cause extreme local erosion, plucking bedrock and creating pothole-type geographical features calledrock-cut basins. Examples can be seen in the flood regions result from glacialLake Missoula, which created thechanneled scablands in theColumbia Basin region of easternWashington.[43]
Wind erosion is a majorgeomorphological force, especially inarid andsemi-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 asdeforestation,urbanization, andagriculture.[44][45]
Wind erosion is of two primary varieties:deflation, where the wind picks up and carries away loose particles; andabrasion, wheresurfaces 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%).[46]: 57 [47]
Wind erosion is much more severe in arid areas and during times of drought. For example, in theGreat 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.[48]
Mass wasting
Awadi inMakhtesh Ramon, Israel, showing gravity collapse erosion on its banks
Mass wasting ormass movement is the downward and outward movement of rock and sediments on a sloped surface, mainly due to the force ofgravity.[49][50]
Mass wasting 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.[51]: 93 It moves material from higher elevations to lower elevations where other eroding agents such as streams andglaciers can then pick up the material and move it to even lower elevations. Mass-wasting processes are always 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 alandslide. 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 rapid rockfall activity is ascree slope, which consists of accumulated loose rock debris at the base of cliffs or steep slopes.[52][53]
Slumping happens on steep hillsides, occurring along distinct fracture zones, often within materials likeclay that, once released, may move quite rapidly downhill. They will often show a spoon-shapedisostatic 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 alonghighways where it is a regular occurrence.[54]
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 (0.02 to 0.04 in) in diameter by wind along the soil surface.[55]
On thecontinental slope, erosion of the ocean floor to create channels andsubmarine canyons can result from the rapid downslope flow ofsediment gravity flows, bodies of sediment-laden water that move rapidly downslope asturbidity currents. Where erosion by turbidity currents creates oversteepened slopes it can also trigger underwater landslides anddebris flows. Turbidity currents can erode channels and canyons into substrates ranging from recently deposited unconsolidated sediments to hard crystalline bedrock.[56][57][58] Almost all continental slopes and deep ocean basins display such channels and canyons resulting from sediment gravity flows and submarine canyons act as conduits for the transfer of sediment from the continents and shallow marine environments to the deep sea.[59][60][61]Turbidites, which are the sedimentary deposits resulting from turbidity currents, comprise some of the thickest and largest sedimentary sequences on Earth, indicating that the associated erosional processes must also have played a prominent role in Earth's history.
The amount and intensity ofprecipitation is the mainclimatic 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 byvegetation. This might be during periods whenagricultural activities leave the soil bare, or insemi-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. themid-western US), rainfall intensity is the primary determinant of erosivity (for a definition oferosivity check,[62]) with higher intensity rainfall generally resulting in more soil erosion by water. The size and velocity ofrain drops is also an important factor. Larger and higher-velocity rain drops have greaterkinetic energy, and thus their impact will displace soil particles by larger distances than smaller, slower-moving rain drops.[63]
In other regions of the world (e.g.western Europe), runoff and erosion result from relatively low intensities ofstratiform 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.[17] According to the climate change projections, erosivity will increase significantly in Europe and soil erosion may increase by 13–22.5% by 2050[64]
InTaiwan, 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 impactsclimate change can have on erosion.[65]
Vegetation acts as an interface between the atmosphere and the soil. It increases thepermeability 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 water[66] and wind erosion. The removal of vegetation increases the rate of surface erosion.[67]
Topography
The topography of the land determines the velocity at whichsurface 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.[63]: 28–30 [68][69]
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 thelower crust andmantle. Because tectonic processes are driven by gradients in the stress field developed in the crust, this unloading can in turn causetectonic orisostatic uplift in the region.[51]: 99 [70] 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 ofNanga Parbat in the westernHimalayas. Such a place has been called a "tectonic aneurysm".[71]
Development
Human land development, in forms including agricultural and urban development, is considered a significant factor in erosion andsediment transport, which aggravatefood insecurity.[72] 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.[65] The intentional removal of soil and rock by humans is a form of erosion that has been namedlisasion.[73]
Mountain ranges take 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 theHimalaya into an almost-flatpeneplain if there are no significantsea-level changes.[74] Erosion of mountains massifs can create a pattern of equally high summits calledsummit accordance.[75] It has been argued thatextension duringpost-orogenic collapse is a more effective mechanism of lowering the height of orogenic mountains than erosion.[76]
Examples of heavily eroded mountain ranges include theTimanides of Northern Russia. Erosion of thisorogen has producedsediments that are now found in theEast European Platform, including the CambrianSablya Formation nearLake Ladoga. Studies of these sediments indicate that it is likely that the erosion of the orogen began in the Cambrian and then intensified in theOrdovician.[77]
If the erosion rate exceedssoil formation, erosion destroys the soil.[78] Lower rates of erosion can prevent the formation ofsoil features that take time to develop.Inceptisols develop on eroded landscapes that, if stable, would have supported the formation of more developedAlfisols.[79]
While erosion of soils is a natural process, human activities have increased by 10–40 times the rate at which erosion occurs globally. Excessive (or accelerated) erosion causes both "on-site" and "off-site" problems. On-site impacts include decreases inagricultural productivity and (onnatural landscapes)ecological collapse, both because of loss of the nutrient-rich uppersoil layers. In some cases, the eventual result isdesertification. Off-site effects includesedimentation of waterways andeutrophication of water bodies, as well as sediment-related damage to roads and houses. Water and wind erosion are the two primary causes ofland degradation; combined, they are responsible for about 84% of the global extent ofdegraded land, making excessive erosion one of the most significantenvironmental problems.[10][80]
Often in the United States, farmers cultivatinghighly erodible land must comply with a conservation plan to be eligible for agricultural assistance.[81]
^ab"Erosion".Encyclopædia Britannica. 2015-12-03.Archived from the original on 2015-12-21. Retrieved2015-12-06.
^Allaby, Michael (2013). "Erosion".A dictionary of geology and earth sciences (Fourth ed.). Oxford University Press.ISBN9780199653065.
^Louvat, P.; Gislason, S. R.; Allegre, C. J. (1 May 2008). "Chemical and mechanical erosion rates in Iceland as deduced from river dissolved and solid material".American Journal of Science.308 (5):679–726.Bibcode:2008AmJS..308..679L.doi:10.2475/05.2008.02.S2CID130966449.
^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.Bibcode:2013Geomo.201....1D.doi:10.1016/j.geomorph.2013.07.021.S2CID129797403.
^Reusser, L.; Bierman, P.; Rood, D. (2015). "Quantifying human impacts on rates of erosion and sediment transport at a landscape scale".Geology.43 (2):171–174.Bibcode:2015Geo....43..171R.doi:10.1130/g36272.1.
^Blanco-Canqui, Humberto; Rattan, Lal (2008). "Soil and water conservation".Principles of soil conservation and management. Dordrecht: Springer. pp. 1–20.ISBN978-1-4020-8709-7.
^abcToy, Terrence J.; Foster, George R.; Renard, Kenneth G. (2002).Soil erosion : processes, prediction, measurement, and control. New York: Wiley.ISBN978-0-471-38369-7.
^See Figure 1 inObreschkow, D.; Dorsaz, N.; Kobel, P.; De Bosset, A.; Tinguely, M.; Field, J.; Farhat, M. (2011). "Confined Shocks inside Isolated Liquid Volumes – A New Path of Erosion?".Physics of Fluids.23 (10): 101702.arXiv:1109.3175.Bibcode:2011PhFl...23j1702O.doi:10.1063/1.3647583.S2CID59437729.
^abFood and Agriculture Organization (1965)."Types of erosion damage".Soil Erosion by Water: Some Measures for Its Control on Cultivated Lands. United Nations. pp. 23–25.ISBN978-92-5-100474-6.
^abBoardman, John; Poesen, Jean, eds. (2007).Soil Erosion in Europe. Chichester: John Wiley & Sons.ISBN978-0-470-85911-7.
^J. Poesen; L. Vandekerckhove; J. Nachtergaele; D. Oostwoud Wijdenes; G. Verstraeten; B. Can Wesemael (2002)."Gully erosion in dryland environments". In Bull, Louise J.; Kirby, M.J. (eds.).Dryland Rivers: Hydrology and Geomorphology of Semi-Arid Channels. John Wiley & Sons. pp. 229–262.ISBN978-0-471-49123-1.
^Borah, Deva K.; et al. (2008)."Watershed sediment yield". In Garcia, Marcelo H. (ed.).Sedimentation Engineering: Processes, Measurements, Modeling, and Practice. ASCE Publishing. p. 828.ISBN978-0-7844-0814-8.
^Geddes, Ian. "Lithosphere". Higher geography for cfe: physical and human environments, Hodder Education, 2015.
^Glynn, Peter W. "Bioerosion and coral-reef growth: a dynamic balance". Life and death of coral reefs (1997): 68–95.
^Bell, Frederic Gladstone. "Marine action and control". Geological hazards: their assessment, avoidance, and mitigation, Taylor & Francis, 1999, pp. 302–306.
^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)
^Gjermundsen, Endre F.; Briner, Jason P.; Akçar, Naki; Foros, Jørn; Kubik, Peter W.; Salvigsen, Otto; Hormes, Anne (2015). "Minimal erosion of Arctic alpine topography during late Quaternary glaciation".Nature Geoscience.8 (10): 789.Bibcode:2015NatGe...8..789G.doi:10.1038/ngeo2524.
^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.
^abNichols, Gary (2009).Sedimentology and Stratigraphy. John Wiley & Sons.ISBN978-1-4051-9379-5.
^Varnes, D.J. (1978). "Slope movement types and processes." In Schuster, R.L., and Krizek, R.J. (Eds.), Landslides: Analysis and Control. Transportation Research Board Special Report 176. National Academy of Sciences.
^Zorn, Matija; Komac, Blaž (2013). "Erosivity". In Bobrowsky, Peter T. (ed.).Encyclopedia of Natural Hazards. Encyclopedia of Earth Sciences Series. Springer Netherlands. pp. 289–290.doi:10.1007/978-1-4020-4399-4_121.ISBN978-90-481-8699-0.
^abBlanco-Canqui, Humberto; Rattan, Lal (2008). "Water erosion".Principles of soil conservation and management. Dordrecht: Springer. pp. 21–53 [29–31].ISBN978-1-4020-8709-7.
^Whisenant, Steve G. (2008)."Terrestrial systems". In Perrow Michael R.; Davy, Anthony J. (eds.).Handbook of Ecological Restoration: Principles of Restoration. Cambridge University Press. p. 89.ISBN978-0-521-04983-2.
^Wainwright, John; Brazier, Richard E. (2011)."Slope systems". In Thomas, David S.G. (ed.).Arid Zone Geomorphology: Process, Form and Change in Drylands. John Wiley & Sons.ISBN978-0-470-71076-0.
^Zeitler, P.K. et al. (2001), Erosion, Himalayan Geodynamics, and the Geomorphology of Metamorphism, GSA Today, 11, 4–9.
^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.Bibcode:2007Caten..69....1C.doi:10.1016/j.catena.2006.04.019.
^Beckinsale, Robert P.; Chorley, Richard J. (2003) [1991]. "Chapter Seven: American Polycyclic Geomorphology".The History of the Study of Landforms. Vol. Three. Taylor & Francis e-Library. pp. 235–236.
^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.Bibcode:1993GSLSP..76..325D.doi:10.1144/gsl.sp.1993.076.01.16.S2CID55985869.
