Editing Erosion (section)

==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 [[Splash (fluid mechanics)|splashed]] by the impact of a single [[raindrop]]]]
[[Rain]]fall, and the [[surface runoff]] which may result from rainfall, produces four main types of [[soil erosion]]: ''splash erosion'', ''[[sheet erosion]]'', ''[[Rill|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).<ref name="toy-2002-p1"/>{{rp|60–61}}<ref>{{cite book|author= Zachar, Dušan|chapter=Classification of soil erosion|title=Soil Erosion|volume=10|publisher=Elsevier|year=1982|isbn=978-0-444-99725-8|page=48|chapter-url=https://books.google.com/books?id=o8ny2dUkpM8C&pg=PA48}}</ref>

In ''splash erosion'', the [[Rain#Raindrop impacts|impact of a falling raindrop]] creates a small crater in the [[soil]],<ref name="Fig. 4">See Figure 1 in {{cite journal |title=Confined Shocks inside Isolated Liquid Volumes – A New Path of Erosion?|journal=Physics of Fluids|volume=23|issue=10|pages=101702|year=2011|arxiv=1109.3175|bibcode=2011PhFl...23j1702O|last1=Obreschkow|first1=D.|last2=Dorsaz|first2=N.|last3=Kobel|first3=P.|last4=De Bosset|first4=A.|last5=Tinguely|first5=M.|last6=Field|first6=J.|last7=Farhat|first7=M.|doi=10.1063/1.3647583|s2cid=59437729}}</ref> ejecting soil particles.<ref name="Hysteretic sediment fluxes in ra"/> The distance these soil particles travel can be as much as {{Convert|0.6|m|ft|abbr=on}} vertically and {{Convert|1.5|m|ft|abbr=on}} horizontally on level ground.

If [[Surface runoff#Saturation excess overland flow|the soil is saturated]], or if the rainfall rate is [[Surface runoff#Infiltration excess overland flow|greater than the rate at which water can infiltrate]] into the soil, surface runoff occurs. If the runoff has sufficient [[Fluid dynamics|flow energy]], it will [[Sediment transport|transport]] loosened soil particles ([[sediment]]) down the slope.<ref name="FAO-1965-pp23-25">{{cite book|author=Food and Agriculture Organization|chapter=Types of erosion damage|title=Soil Erosion by Water: Some Measures for Its Control on Cultivated Lands|publisher=United Nations|year=1965|isbn=978-92-5-100474-6|pages=23–25|chapter-url=https://books.google.com/books?id=6KeL3ix6ZqQC&pg=PA23}}</ref> ''[[Sheet erosion]]'' is the transport of loosened soil particles by overland flow.<ref name="FAO-1965-pp23-25" />
[[File:Rummu aherainemägi2.jpg|thumb|A [[spoil 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 exhibit [[hydraulic]] physics very different from water flowing through the deeper, wider channels of streams and rivers.<ref>{{cite journal | last1 = Nearing | first1 = M.A. | last2 = Norton | first2 = L.D. | last3 = Bulgakov | first3 = D.A. | last4 = Larionov | first4 = G.A. | last5 = West | first5 = L.T. | last6 = Dontsova | first6 = K.M. | year = 1997 | title = Hydraulics and erosion in eroding rills | journal = Water Resources Research | volume = 33 | issue = 4| pages = 865–876 | doi=10.1029/97wr00013|bibcode = 1997WRR....33..865N | doi-access = free }}</ref>

{{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.<ref name=Boardman>{{cite book|editor-last1=Boardman|editor-first1=John|editor-last2=Poesen|editor-first2=Jean|title=Soil Erosion in Europe|date=2007|publisher=John Wiley & Sons|location=Chichester|isbn=978-0-470-85911-7}}</ref><ref>{{cite book |author=J. Poesen |author2=L. Vandekerckhove |author3=J. Nachtergaele |author4=D. Oostwoud Wijdenes |author5=G. Verstraeten |author6=B. Can Wesemael |chapter=Gully erosion in dryland environments|pages=229–262|editor=Bull, Louise J. |editor2=Kirby, M.J.|title=Dryland Rivers: Hydrology and Geomorphology of Semi-Arid Channels|publisher=John Wiley & Sons|year=2002|isbn=978-0-471-49123-1|chapter-url=https://books.google.com/books?id=qjHoYZXQee0C&pg=PA229}}</ref><ref>{{cite book|author=Borah, Deva K.|chapter=Watershed sediment yield|editor=Garcia, Marcelo H.|title=Sedimentation Engineering: Processes, Measurements, Modeling, and Practice|publisher=ASCE Publishing|year=2008|isbn=978-0-7844-0814-8|page=828|chapter-url=https://books.google.com/books?id=1AsypwBUa_wC&pg=PA828|display-authors=etal}}</ref> 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.<ref>{{Cite journal|last1=Vanmaercke|first1=Matthias|last2=Panagos|first2=Panos|last3=Vanwalleghem|first3=Tom|last4=Hayas|first4=Antonio|last5=Foerster|first5=Saskia|last6=Borrelli|first6=Pasquale|last7=Rossi|first7=Mauro|last8=Torri|first8=Dino|last9=Casali|first9=Javier|last10=Borselli|first10=Lorenzo|last11=Vigiak|first11=Olga|date=July 2021|title=Measuring, modelling and managing gully erosion at large scales: A state of the art|url=https://linkinghub.elsevier.com/retrieve/pii/S0012825221001379|journal=Earth-Science Reviews|language=en|volume=218|pages=103637|doi=10.1016/j.earscirev.2021.103637|bibcode=2021ESRv..21803637V|hdl=10198/24417|s2cid=234800558|hdl-access=free}}</ref>

Extreme gully erosion can progress to formation of [[badlands]]. These form under conditions of high relief on [[Erodability|easily eroded bedrock]] in climates favorable to erosion. Conditions or disturbances that limit the growth of protective vegetation ([[biorhexistasy|rhexistasy]]) are a key element of badland formation.<ref>{{cite journal |last1=Moreno-de las Heras |first1=Mariano |last2=Gallart |first2=Francesc |title=The Origin of Badlands |journal=Badlands Dynamics in a Context of Global Change |date=2018 |pages=27–59 |doi=10.1016/B978-0-12-813054-4.00002-2|isbn=9780128130544 }}</ref>

===Rivers and streams===

{{further|topic=water's erosive ability|Hydraulic action}}
[[File: Dobbingstone Burn - geograph.org.uk - 1291882.jpg|thumb|Dobbingstone [[Burn (landform)|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 till]] that was left behind as ice age glaciers flowed over the terrain.]]
[[File:Tauglbach 4.JPG|thumb|Layers of [[chalk]] exposed by a river eroding through them]]
[[File:Green land soil erosion.jpg|alt=Green land erosion |thumb|Green land erosion]]
''Valley'' or ''stream erosion'' occurs with continued water flow along a [[Linear feature extraction|linear feature.]] The erosion is both [[Downcutting|downward]], deepening the [[valley]], and [[headward erosion|headward]], extending the valley into the hillside, creating [[Head cut (stream geomorphology)|head 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 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 [[meander]]s 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, [[pebble]]s, and [[boulder]]s can also act erosively as they traverse a surface, in a process known as ''traction''.<ref>Ritter, Michael E. (2006) [http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/fluvial_systems/geologic_work_of_streams.html "Geologic Work of Streams"] {{webarchive|url=https://web.archive.org/web/20120506040721/http://www4.uwsp.edu/geo/faculty/ritter/geog101/textbook/fluvial_systems/geologic_work_of_streams.html |date=2012-05-06 }} ''The Physical Environment: an Introduction to Physical Geography'' University of Wisconsin, {{OCLC|79006225}}</ref>

''[[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 [[River bank failure|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.<ref>{{Cite book |chapter-url=https://books.google.com/books?id=_PJHw-hSKGgC&pg=PA113 |title=Stream hydrology: an introduction for ecologists |author=Nancy D. Gordon |chapter=Erosion and Scour |isbn=978-0-470-84357-4 |date=2004 |publisher=John Wiley and Sons }}</ref>

''Thermal erosion'' is the result of melting and weakening [[permafrost]] due to moving water.<ref name="nsidc_thermal">{{cite web|url=http://nsidc.org/cgi-bin/words/word.pl?thermal%20erosion |title=Thermal Erosion |work=NSIDC Glossary |publisher=[[National Snow and Ice Data Center]] |access-date=21 December 2009 |archive-url=https://web.archive.org/web/20101218124656/http://nsidc.org/cgi-bin/words/word.pl?thermal%20erosion |archive-date=2010-12-18 |url-status=live }}</ref> 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.<ref name="lena">{{cite journal|doi=10.1002/esp.592|title=Fluvial thermal erosion investigations along a rapidly eroding river bank: application to the Lena River (central Siberia)|year=2003|last1=Costard|first1=F.|last2=Dupeyrat|first2=L.|last3=Gautier|first3=E.|last4=Carey-Gailhardis|first4=E.|journal=[[Earth Surface Processes and Landforms]]|volume=28|pages=1349–1359|bibcode = 2003ESPL...28.1349C|issue=12 |s2cid=131318239 }}</ref> Much of this erosion occurs as the weakened banks fail in large slumps. Thermal erosion also affects the [[Arctic Ocean|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.<ref name="jones_arctic">{{cite journal|last=Jones|first=B.M.|author2=Hinkel, K.M.|author3=Arp, C.D.|author4=Eisner, W.R.|year=2008|title=Modern Erosion Rates and Loss of Coastal Features and Sites, Beaufort Sea Coastline, Alaska|journal=Arctic|volume=61|issue=4|pages=361–372|url=http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/44/115|doi=10.14430/arctic44|url-status=dead|archive-url=https://web.archive.org/web/20130517101602/http://arctic.synergiesprairies.ca/arctic/index.php/arctic/article/view/44/115|archive-date=2013-05-17|hdl=10535/5534|hdl-access=free}}</ref>

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]],<ref name="mont">{{cite journal|last=Montgomery|first=David R.|author2=Stolar, Drew B. |title=Reconsidering Himalayan river anticlines|journal=Geomorphology|date=1 December 2006|volume=82|issue=1–2|pages=4–15|doi=10.1016/j.geomorph.2005.08.021|bibcode = 2006Geomo..82....4M }}</ref> as [[isostatic rebound]] raises rock beds unburdened by erosion of overlying beds.

===Coastal erosion===
{{main|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 [[Southerndown]] in South Wales]]
[[File:Erosion of Boulder Clay in Filey Bay.JPG|thumb|Erosion of the [[boulder clay]] (of [[Pleistocene]] age) along cliffs of [[Filey]] Bay, Yorkshire, England]]
Shoreline erosion, which occurs on both exposed and sheltered coasts, primarily occurs through the action of currents and [[ocean surface wave|waves]] but sea level (tidal) change can also play a role.
[[File:Sea dune Erosion at Talace, Wales.webm|thumb|Sea-dune erosion at [[Talacre]] beach, [[Wales]]]]

''[[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 (geology)|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.<ref>Geddes, Ian. "Lithosphere". Higher geography for cfe: physical and human environments, Hodder Education, 2015.</ref> [[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 beach|shingle]] and sand. Another significant source of erosion, particularly on carbonate coastlines, is boring, scraping and grinding of organisms, a process termed ''[[bioerosion]]''.<ref>Glynn, Peter W. "Bioerosion and coral-reef growth: a dynamic balance". Life and death of coral reefs (1997): 68–95.</ref>

[[Sediment]] is transported along the coast in the direction of the prevailing current ([[longshore drift]]). When the upcurrent [[Coastal sediment supply|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 (geology)|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 (landform)|spit]]). [[Armor (hydrology)|Armoured]] beaches and submerged offshore [[shoal|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.<ref>Bell, Frederic Gladstone. "Marine action and control". Geological hazards: their assessment, avoidance, and mitigation, Taylor & Francis, 1999, pp. 302–306.</ref>

Erosion of a coastal surface, followed by a fall in sea level, can produce a distinctive landform called a [[raised beach]].<ref name="Pinter2010">{{cite web| last1=Pinter |first1=N |date=2010 |title=Exercise 6 - Coastal Terraces, Sealevel, and Active Tectonics |url=http://www.geology.siu.edu/people/pinter/pdf/CoastalExercise.pdf |access-date=2011-04-21 |url-status=dead |archive-url=https://web.archive.org/web/20101010230028/http://www.geology.siu.edu/people/pinter/pdf/CoastalExercise.pdf |archive-date=2010-10-10 }}</ref>

===Chemical erosion===
{{see also|Karst topography}}
<!--why is chemical erosion listed here as a physical (mechanical) process?-->
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.<ref>{{cite journal |last1=Dixon |first1=John C. |last2=Thorn |first2=Colin E. |date=2005 |title=Chemical weathering and landscape development in mid-latitude alpine environments |journal=[[Geomorphology (journal)|Geomorphology]] |volume=67 |issue=1–2 |pages=127–145 |doi= 10.1016/j.geomorph.2004.07.009|bibcode = 2005Geomo..67..127D }}</ref>

Formation of [[sinkhole]]s and other features of karst topography is an example of extreme chemical erosion.<ref>{{cite journal|author = Lard, L. |author2=Paull, C. |author3=Hobson, B. |year = 1995|title = Genesis of a submarine sinkhole without subaerial exposure|journal = Geology|volume = 23|issue = 10|pages = 949–951|doi = 10.1130/0091-7613(1995)023<0949:GOASSW>2.3.CO;2|bibcode = 1995Geo....23..949L }}</ref>

===Glaciers===
[[File:Pirunpesä Jalasjärvi 8.JPG|thumb|left|[[The Devil's Nest]] (''Pirunpesä''), the deepest ground erosion in [[Europe]],<ref>{{cite web| url = https://www.pizzatravel.com.ua/eng/finland/117/devils_nest| title = The Devil's Nest, the deepest ground erosion in Europe}}</ref> located in [[Jalasjärvi]], [[Kurikka]], [[Finland]]]]
[[File:MorainesLakeLouise.JPG|thumb|right|Glacial [[moraines]] above [[Lake Louise, Alberta|Lake Louise]], in [[Alberta, Canada]]]]
[[Glacier]]s erode predominantly by three different processes: abrasion/scouring, [[Plucking (glaciation)|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 valley]]s. 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.<ref>{{Cite journal|last1=Harbor|first1=Jonathan M.|last2=Hallet|first2=Bernard|last3=Raymond|first3=Charles F.|date=1988-05-26|title=A numerical model of landform development by glacial erosion|journal=Nature|language=en|volume=333|issue=6171|pages=347–349|doi=10.1038/333347a0|bibcode=1988Natur.333..347H|s2cid=4273817}}</ref>

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&nbsp;m.<ref>{{Cite journal|last1=Egholm|first1=D. L.|last2=Nielsen|first2=S. B.|last3=Pedersen|first3=V.K.|last4=Lesemann|first4=J.-E.|title=Glacial effects limiting mountain height|journal=Nature|volume=460|issue=7257|pages=884–887|doi=10.1038/nature08263|pmid=19675651|bibcode=2009Natur.460..884E|year=2009|s2cid=205217746}}</ref> 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.<ref name="reference">{{cite journal | last1 = Thomson | first1 = Stuart N. | last2 = Brandon | first2 = Mark T. | last3 = Tomkin | first3 = Jonathan H. | last4 = Reiners | first4 = Peter W. | last5 = Vásquez | first5 = Cristián | last6 = Wilson | first6 = Nathaniel J. | year = 2010 | title = Glaciation as a destructive and constructive control on mountain building | journal = Nature | volume = 467 | issue = 7313| pages = 313–317 | doi = 10.1038/nature09365 | pmid = 20844534 |bibcode = 2010Natur.467..313T | s2cid = 205222252 | hdl = 10533/144849 | hdl-access = free }}</ref> As mountains grow higher, they generally allow for more glacial activity (especially in the [[accumulation zone]] above the glacial equilibrium line altitude),<ref>{{cite journal | last1 = Tomkin | first1 = J.H. | last2 = Roe | first2 = G.H. | year = 2007 | title = Climate and tectonic controls on glaciated critical-taper orogens | url = http://earthweb.ess.washington.edu/roe/Publications/TomkinRoe_Glaciers_EPSL07.pdf | journal = Earth Planet. Sci. Lett. | volume = 262 | issue = 3–4 | pages = 385–397 | doi = 10.1016/j.epsl.2007.07.040 | bibcode = 2007E&PSL.262..385T | citeseerx = 10.1.1.477.3927 | access-date = 2017-10-24 | archive-url = https://web.archive.org/web/20170809121522/http://earthweb.ess.washington.edu/roe/Publications/TomkinRoe_Glaciers_EPSL07.pdf | archive-date = 2017-08-09 | url-status=live }}</ref> which causes increased rates of erosion of the mountain, decreasing mass faster than [[isostatic rebound]] can add to the mountain.<ref>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)</ref> 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''.<ref name="reference"/> 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.<ref>{{Cite journal|last1=Gjermundsen|first1=Endre F.|last2=Briner|first2=Jason P.|last3=Akçar|first3=Naki|last4=Foros|first4=Jørn|last5=Kubik|first5=Peter W.|last6=Salvigsen|first6=Otto|last7=Hormes|first7=Anne|title=Minimal erosion of Arctic alpine topography during late Quaternary glaciation|journal=Nature Geoscience|volume=8|issue=10|pages=789|doi=10.1038/ngeo2524|bibcode=2015NatGe...8..789G|year=2015}}</ref>

These processes, combined with erosion and transport by the water network beneath the glacier, leave behind [[glacial landform]]s such as [[moraine]]s, [[drumlin]]s, ground moraine (till), [[glaciokarst]], kames, kame deltas, moulins, and [[glacial erratic]]s in their wake, typically at the terminus or during [[Retreat of glaciers since 1850|glacier retreat]].<ref>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. EBSCO''host''.</ref>

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.<ref>{{Cite journal|last1=Prasicek|first1=Günther|last2=Larsen|first2=Isaac J.|last3=Montgomery|first3=David R.|date=2015-08-14|title=Tectonic control on the persistence of glacially sculpted topography|journal=Nature Communications|language=en|volume=6|doi=10.1038/ncomms9028|issn=2041-1723| pmc=4557346 |pmid=26271245|page=8028|bibcode=2015NatCo...6.8028P |bibcode-access=free |doi-access=free }}</ref>

===Floods===
[[File:Seaton Beach after heavy rainfall.jpg|alt=The mouth of the River Seaton in Cornwall after heavy rainfall caused flooding in the area and cause a significant amount of the beach to erode|thumb|The mouth of the [[River Seaton]] in [[Cornwall]] 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, [[Kolk (vortex)|kolks]], or [[vortex|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 basin]]s. Examples can be seen in the flood regions result from glacial [[Lake Missoula]], which created the [[channeled scablands]] in the [[Columbia River Drainage Basin|Columbia Basin]] region of eastern [[Washington (state)|Washington]].<ref>See, for example: {{cite book|author=Alt, David|title=Glacial Lake Missoula & its Humongous Floods
|publisher=Mountain Press|year=2001|isbn=978-0-87842-415-3|url=https://books.google.com/books?id=s4y3c8fxeEwC}}</ref>

===Wind erosion===
[[File:Im Salar de Uyuni.jpg|thumb|[[Árbol de Piedra]], a rock formation in the [[Altiplano]], [[Bolivia]] sculpted by wind erosion]]
{{main|Aeolian processes}}
Wind erosion is a major [[geomorphological]] force, especially in [[arid region|arid]] and [[semi-arid region|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]].<ref>{{Cite book|author=Zheng, Xiaojing |author2=Huang, Ning|title=Mechanics of Wind-Blown Sand Movements|publisher=Springer|year=2009|isbn=978-3-540-88253-4|pages=7–8|url=https://books.google.com/books?id=R6kYrbA3XSAC&pg=PA7|bibcode=2009mwbs.book.....Z}}</ref><ref>{{cite book|author=Cornelis, Wim S.|chapter=Hydroclimatology of wind erosion in arid and semi-arid environments|editor=D'Odorico, Paolo |editor2=Porporato, Amilcare|title=Dryland Ecohydrology|publisher=Springer|year=2006|isbn=978-1-4020-4261-4|page=141|chapter-url=https://books.google.com/books?id=rUsUPZbFHK8C&pg=PA141}}</ref>

Wind erosion is of two primary varieties: ''[[Aeolian processes#Wind erosion|deflation]]'', where the wind picks up and carries away loose particles; and ''[[Abrasion (geology)|abrasion]]'', where [[Erosion surface|surfaces]] are worn down as they are struck by airborne particles carried by wind. Deflation is divided into three categories: (1) ''[[Downhill creep|surface creep]]'', where larger, heavier particles slide or roll along the ground; (2) ''[[Saltation (geology)|saltation]]'', where particles are lifted a short height into the air, and bounce and saltate across the surface of the soil; and (3) ''[[Suspension (chemistry)|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%).<ref name=BlancoWind>{{cite book|last1=Blanco-Canqui|first1=Humberto|last2=Rattan|first2=Lal|chapter=Wind erosion|title=Principles of soil conservation and management|date=2008|publisher=Springer|location=Dordrecht|isbn=978-1-4020-8709-7|pages=54–80}}</ref>{{rp|57}}<ref>{{Cite book|author=Balba, A. Monem|chapter=Desertification: Wind erosion|title=Management of Problem Soils in Arid Ecosystems|publisher=CRC Press|year=1995|isbn=978-0-87371-811-0|page=214|chapter-url=https://books.google.com/books?id=uS62XNzDZDsC&pg=PA214}}</ref>

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.<ref>{{Cite book|author=Wiggs, Giles F.S.|chapter=Geomorphological hazards in drylands|editor=Thomas, David S.G.|title=Arid Zone Geomorphology: Process, Form and Change in Drylands|publisher=John Wiley & Sons|year=2011|isbn=978-0-470-71076-0|page=588|chapter-url=https://books.google.com/books?id=swz4rh4KaLYC&pg=PA588}}</ref>

===Mass wasting===
[[File:NegevWadi2009.JPG|thumb|A [[wadi]] in [[Makhtesh Ramon]], Israel, showing gravity collapse erosion on its banks]]
{{Main|Mass wasting}}
''Mass wasting'' or ''mass movement'' is the downward and outward movement of rock and sediments on a sloped surface, mainly due to the force of [[gravity]].<ref>{{cite book|author=Van Beek, Rens|chapter=Hillside processes: mass wasting, slope stability, and erosion|editor=Norris, Joanne E. |display-editors=etal |title=Slope Stability and Erosion Control: Ecotechnological Solutions|publisher=Springer|year=2008|isbn=978-1-4020-6675-7|chapter-url=https://books.google.com/books?id=YWPcffxM_A0C&pg=PA17|bibcode=2008ssec.conf.....N}}</ref><ref>{{cite book|author=Gray, Donald H. |author2=Sotir, Robbin B.|chapter=Surficial erosion and mass movement|title=Biotechnical and Soil Bioengineering Slope Stabilization: A Practical Guide for Erosion Control|publisher=John Wiley & Sons|year=1996|isbn=978-0-471-04978-4|page=20|chapter-url=https://books.google.com/books?id=kCbp6IvFHrAC&pg=20}}</ref>

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.<ref name=Nichols>{{cite book|author=Nichols, Gary|title=Sedimentology and Stratigraphy|publisher=John Wiley & Sons|year=2009|isbn=978-1-4051-9379-5}}</ref>{{rp|93}} It moves material from higher elevations to lower elevations where other eroding agents such as streams and [[glacier]]s 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 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}}

''[[Slump (geology)|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 [[highway]]s where it is a regular occurrence.<ref name="P.2007">{{cite book|author=Sivashanmugam, P.|title=Basics of Environmental Science and Engineering|url=https://books.google.com/books?id=aTJ31ycKQeEC&pg=PA43|year=2007|publisher=New India Publishing|isbn=978-81-89422-28-8|pages=43–}}</ref>

''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.<ref>{{Cite web|url=http://library.eb.com/levels/referencecenter/article/27828|title=Britannica Library|website=library.eb.com|language=en|access-date=2017-01-31}}</ref>

===Submarine sediment gravity flows===
[[File:CanyonsbathyLG USGS.jpg|thumb|[[Bathymetry]] of submarine canyons in the [[continental slope]] off the coast of New York and New Jersey]]
On the [[continental slope]], erosion of the ocean floor to create channels and [[submarine canyon]]s can result from the rapid downslope flow of [[sediment gravity flow]]s, bodies of sediment-laden water that move rapidly downslope as [[turbidity current]]s. Where erosion by turbidity currents creates oversteepened slopes it can also trigger underwater landslides and [[debris flow]]s. Turbidity currents can erode channels and canyons into substrates ranging from recently deposited unconsolidated sediments to hard crystalline bedrock.<ref>{{cite journal |last1=Halsey |first1=Thomas C. |title=Erosion of unconsolidated beds by turbidity currents |journal=Physical Review Fluids |date=15 October 2018 |volume=3 |issue=10 |pages=104303 |doi=10.1103/PhysRevFluids.3.104303|bibcode=2018PhRvF...3j4303H |s2cid=134740576 }}</ref><ref>{{cite journal |last1=Mitchell |first1=Neil C. |title=Bedrock erosion by sedimentary flows in submarine canyons |journal=Geosphere |date=October 2014 |volume=10 |issue=5 |pages=892–904 |doi=10.1130/GES01008.1|bibcode=2014Geosp..10..892M |doi-access=free }}</ref><ref>{{cite journal |last1=Smith |first1=M. Elliot |last2=Werner |first2=Samuel H. |last3=Buscombe |first3=Daniel |last4=Finnegan |first4=Noah J. |last5=Sumner |first5=Esther J. |last6=Mueller |first6=Erich R. |title=Seeking the Shore: Evidence for Active Submarine Canyon Head Incision Due to Coarse Sediment Supply and Focusing of Wave Energy |journal=Geophysical Research Letters |date=28 November 2018 |volume=45 |issue=22 |pages=12,403–12,413 |doi=10.1029/2018GL080396|bibcode=2018GeoRL..4512403S |s2cid=134823668 |doi-access=free }}</ref> 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.<ref>{{cite journal |last1=Harris |first1=Peter T. |title=Seafloor geomorphology—coast, shelf, and abyss |journal=Seafloor Geomorphology as Benthic Habitat |date=2020 |pages=115–160 |doi=10.1016/B978-0-12-814960-7.00006-3|isbn=9780128149607 }}</ref><ref>{{cite journal |last1=Bührig |first1=Laura H. |last2=Colombera |first2=Luca |last3=Patacci |first3=Marco |last4=Mountney |first4=Nigel P. |last5=McCaffrey |first5=William D. |title=A global analysis of controls on submarine-canyon geomorphology |journal=Earth-Science Reviews |date=October 2022 |volume=233 |pages=104150 |doi=10.1016/j.earscirev.2022.104150|bibcode=2022ESRv..23304150B |s2cid=251576822 |doi-access=free }}</ref><ref>{{cite book |title=Seafloor Geomorphology as Benthic Habitat |date=2012 |doi=10.1016/C2010-0-67010-6|isbn=9780123851406 |s2cid=213281574 }}</ref> [[Turbidite]]s, 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.