Editing Aeolian processes

{{short description|Processes due to wind activity}}
{{Use dmy dates|date=April 2022}}
[[File:Erosioenparamo.jpg|thumb|Wind erosion of soil at the foot of [[Chimborazo (volcano)|Chimborazo]], Ecuador]]
[[File:Ventifact 1871 USGS.jpg|thumb|Rock carved by drifting sand below [[Fortification Rock]] in Arizona (Photo by [[Timothy H. O'Sullivan]], USGS, 1871)]]

'''Aeolian processes''', also spelled '''eolian''',<ref name=Allaby2013>{{cite book |last1=Allaby |first1=Michael |title=A dictionary of geology and earth sciences |date=2013 |publisher=Oxford University Press |location=Oxford |isbn=9780199653065 |edition=Fourth |chapter=aeolian processes (eolian processes)}}</ref> pertain to [[wind]] activity in the study of [[geology]] and [[weather]] and specifically to the wind's ability to shape the surface of the [[Earth]] (or other [[planet]]s).  Winds may [[erosion|erode]], transport, and deposit materials. They are effective agents in regions with sparse [[vegetation]], a lack of soil moisture and a large supply of unconsolidated [[sediment]]s. Although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as [[desert]]s.<ref>{{cite web |url=https://pubs.usgs.gov/gip/deserts/eolian/ |website=Deserts: Geology and Resources |title=Eolian Processes |publisher=United States Geological Survey |access-date=24 August 2020 |date=1997}}</ref>

The term is derived from the name of the [[Greek god]] [[Aeolus#Aeolus (son of Hippotes)|Aeolus]], the keeper of the winds.<ref>{{cite web |title=Aeolian |url=https://www.dictionary.com/browse/aeolian |website=Dictionary.com |publisher=Dictionary.com LLC |access-date=24 August 2020 |date=2020}}</ref><ref>{{oed|aeolian}}</ref>

==Definition and setting==
''Aeolian processes'' are those processes of [[erosion]], [[Sediment transport|transport]], and [[Deposition (geology)|deposition]] of [[sediment]]s that are caused by wind at or near the surface of the earth.<ref name=Allaby2013/> Sediment deposits produced by the action of wind and the [[sedimentary structures]] characteristic of these deposits are also described as ''aeolian''.<ref name=Jackson1997>{{cite book |editor1-last=Jackson |editor1-first=Julia A. |title=Glossary of geology. |date=1997 |publisher=American Geological Institute |location=Alexandria, Virginia |isbn=0922152349 |edition=Fourth |chapter=eolian}}</ref>

Aeolian processes are most important in areas where there is little or no vegetation.<ref name=Allaby2013/> However, aeolian deposits are not restricted to arid climates. They are also seen along shorelines; along stream courses in semiarid climates; in areas of ample sand weathered from weakly cemented [[sandstone]] outcrops; and in areas of [[glacial outwash]].<ref name=Thornbury1969/>

[[Loess]], which is [[silt]] deposited by wind, is common in humid to subhumid climates. Much of North America and Europe are underlain by sand and loess of [[Pleistocene]] age originating from glacial outwash.<ref name=Thornbury1969>{{cite book |last1=Thornbury |first1=William D. |title=Principles of geomorphology |date=1969 |publisher=Wiley |location=New York |isbn=0471861979 |pages=292–300 |edition=2nd}}</ref>

The lee (downwind) side of river valleys in semiarid regions are often blanketed with sand and sand dunes. Examples in North America include the [[Platte River|Platte]], [[Arkansas River|Arkansas]], and [[Missouri River|Missouri]] Rivers.<ref name=Thornbury1969/>

==Wind erosion==
<!-- [[Aeolian erosion]] links here, as does [[Wind erosion]] -->
[[File:KelsoSand.JPG|thumb|Sand blowing off a crest in the [[Kelso Dunes]] of the [[Mojave Desert]], California]]
[[File:Cheops Pyramid wind erosion.jpg|thumb|Effects of wind erosion at Giza pyramid, May 1972]]
Wind [[erosion|erodes]] the Earth's surface by ''deflation'' (the removal of loose, fine-grained particles by the [[turbulence|turbulent]] action of the wind) and by ''[[ventifact|abrasion]]'' (the wearing down of surfaces by the grinding action and [[sandblasting]] by windborne particles). Once [[Entrainment (physical geography)|entrained]] in the wind, collisions between particles further break them down, a process called ''attrition''.{{sfn|Thornbury|1969|pp=288–294}}

Worldwide, erosion by water is more important than erosion by wind, but wind erosion is important in semiarid and arid regions.<ref>{{cite book |last1=Lal |first1=R. |title=Soil erosion research methods |date=2017 |publisher=Routledge |location=Milton, United Kingdom |isbn=9780203739358 |edition=0002 |chapter=Soil Erosion by Wind and Water: Problems and Prospects}}</ref> Wind erosion is increased by some human activities, such as the use of [[4x4 vehicles]].<ref>{{cite journal |last1=Retta |first1=A. |last2=Wagner |first2=L.E. |last3=Tatarko |first3=J. |title=Military Vehicle Trafficking Impacts on Vegetation and Soil Bulk Density at Fort Benning, Georgia |url=https://infosys.ars.usda.gov/WindErosion/publications/pdf/Military%20Vehicle%20Trafficking%20Impacts%20on%20Vegetation%20and%20Soil%20Bulk%20Density%20at%20Fort%20Benning%20Georgia.pdf |access-date=14 January 2016 |journal=Transactions of the ASABE |year=2014 |volume=57 |issue=4 |pages=1043–1055 |issn=2151-0032 |doi=10.13031/trans.57.10327|s2cid=9602605 }}</ref>

===Deflation===
Deflation is the lifting and removal of loose material from the surface by wind turbulence.{{sfn|Thornbury|1969|p=289}}{{sfn|Jackson|1997|loc="deflation"}} It takes place by three mechanisms: traction/surface creep, [[Saltation (geology)|saltation]], and suspension. Traction or surface creep is a process of larger grains sliding or rolling across the surface. Saltation refers to particles bouncing across the surface for short distances. Suspended particles are fully entrained in the wind, which carries them for long distances.<ref name=Boggs2006>{{cite book |last1=Boggs |first1=Sam |title=Principles of sedimentology and stratigraphy |date=2006 |publisher=Pearson Prentice Hall |location=Upper Saddle River, N.J. |isbn=0131547283 |edition=4th |pages=258–268}}</ref> Saltation likely accounts for 50–70 % of deflation, while suspension accounts for 30–40 % and surface creep accounts for 5–25 %.<ref name="ZhengWang2014">{{cite book |last1=Zheng |first1=Fenli |last2=Wang |first2=Bin |chapter=Soil Erosion in the Loess Plateau Region of China |title=Restoration and Development of the Degraded Loess Plateau, China |series=Ecological Research Monographs |date=2014 |pages=77–92 |doi=10.1007/978-4-431-54481-4_6|isbn=978-4-431-54480-7 }}</ref>

Regions which experience intense and sustained erosion are called deflation zones.<ref name="JolivetEta2021">{{cite journal |last1=Jolivet |first1=M. |last2=Braucher |first2=R. |last3=Dovchintseren |first3=D. |last4=Hocquet |first4=S. |last5=Schmitt |first5=J.-M. |title=Erosion around a large-scale topographic high in a semi-arid sedimentary basin: Interactions between fluvial erosion, aeolian erosion and aeolian transport |journal=Geomorphology |date=August 2021 |volume=386 |pages=107747 |doi=10.1016/j.geomorph.2021.107747|bibcode=2021Geomo.38607747J |s2cid=234855671 |url=https://hal-insu.archives-ouvertes.fr/insu-03203903/file/jolivet-proof-2021.pdf }}</ref> Most aeolian deflation zones are composed of [[desert pavement]], a sheet-like surface of rock fragments that remains after wind and water have removed the fine particles. The rock mantle in desert pavements protects the underlying material from further deflation. Areas of desert pavement form the ''regs'' or stony deserts of the [[Sahara]]. These are further divided into rocky areas called ''[[hamada]]s'' and areas of small rocks and gravel called ''serirs''.{{sfn|Thornbury|1969|pp=288–294}} Desert pavement is extremely common in desert environments.<ref name="Cooke1993">{{cite book |last1=Cooke |first1=Ronald U. |title=Desert geomorphology |date=1993 |publisher=UCL Press |location=London |isbn=9780203020593 |page=68 |url=https://books.google.com/books?id=WOcUNbRUGtwC&q=desert+pavement&pg=PA68 |access-date=8 March 2022}}</ref>

[[blowout (geology)|Blowout]]s are hollows formed by wind deflation. Blowouts are generally small, but may be up to several kilometers in diameter. The smallest are mere dimples {{convert|1|ft|sigfig=1|sp=us|order=flip}} deep and {{convert|10|ft|order=flip|sigfig=1|sp=us}} in diameter. The largest include the blowout hollows of Mongolia, which can be {{convert|5|mi|order=flip|sigfig=1|sp=us}} across and {{convert|200 to 400|feet|order=flip|sigfig=1|sp=us}} deep. [[The Big Hollow (Wyoming)|Big Hollow]] in [[Wyoming]], US, extends {{convert|9 by 6|mi|order=flip|sigfig=2|sp=us}} and is up to {{convert|300|ft|order=flip|sigfig=1|sp=us}} deep.{{sfn|Thornbury|1969|pp=288–294}}

===Abrasion===
[[File:Yardangs in the Tsaidam Desert.jpg|thumb|right|300px|Yardangs in the [[Qaidam]] Desert, [[Qinghai Province]], China]]
{{See also|Abrasion (geology)}}

Abrasion (also sometimes called ''corrasion'') is the process of wind-driven grains knocking or wearing material off of [[landform]]s. It was once considered a major contributor to desert erosion, but by the mid-20th Century, it had come to be considered much less important. Wind can normally lift sand only a short distance, with most windborne sand remaining within {{convert|50|cm|sigfig=1|sp=us}} of the surface and practically none normally being carried above {{convert|6|ft|sigfig=1|order=flip|sp=us}}. Many desert features once attributed to wind abrasion, including wind caves, [[mushroom rock]]s, and the honeycomb weathering called [[tafoni]], are now attributed to differential weathering, rainwash, deflation rather than abrasion, or other processes.{{sfn|Thornbury|1969|pp=288–294}}

''[[Yardang]]s'' are one kind of desert feature that is widely attributed to wind abrasion. These are rock ridges, up to tens of meters high and kilometers long, that have been streamlined by desert winds. Yardangs characteristically show elongated furrows or grooves aligned with the prevailing wind. They form mostly in softer material such as silts.{{sfn|Thornbury|1969|pp=288–294}}

Abrasion produces polishing and pitting, grooving, shaping, and faceting of exposed surfaces. These are widespread in arid environments but geologically insignificant. Polished or faceted surfaces called ''[[ventifacts]]'' are rare, requiring abundant sand, powerful winds, and a lack of vegetation for their formation.{{sfn|Thornbury|1969|pp=288–294}}

In parts of Antarctica wind-blown snowflakes that are technically sediments have also caused abrasion of exposed rocks.<ref>National Geographic Almanac of Geography, 2005, page 166, {{ISBN|0-7922-3877-X}}.</ref>

===Attrition===
Attrition is the wearing down by collisions of particles entrained in a moving fluid.{{sfn|Jackson|1997|loc="attrition"}}<ref name=Leeder2011/> It is effective at rounding sand grains and at giving them a distinctive ''frosted'' surface texture.<ref>{{cite journal |last1=Margolis |first1=Stanley V. |last2=Krinsley |first2=David H. |title=Submicroscopic Frosting on Eolian and Subaqueous Quartz Sand Grains |journal=Geological Society of America Bulletin |date=1971 |volume=82 |issue=12 |pages=3395 |doi=10.1130/0016-7606(1971)82[3395:SFOEAS]2.0.CO;2}}</ref>

Collisions between windborne particles is a major source of dust in the size range of 2-5 microns. Most of this is produced by the removal of a weathered [[clay]] coating from the grains.<ref name=Leeder2011>{{cite book |last1=Leeder |first1=M. R. |title=Sedimentology and sedimentary basins : from turbulence to tectonics |date=2011 |publisher=Wiley-Blackwell |location=Chichester, West Sussex, UK |isbn=9781405177832 |edition=2nd |pages=24–25}}</ref>

==Transport==
{{see also|Aeolian dust}}
[[File:Dust storm in Spearman,Texas, 1935-04-14.jpg|thumb|[[Dust storm]] approaching [[Spearman, Texas]], 14 April 1935]]
[[File:Dust storm, Amarillo, Texas, 8b27554a.jpg|thumb|[[Dust storm]] in [[Amarillo, Texas]]. FSA photo by [[Arthur Rothstein]] (1936)]]
[[File:Sandstorm in Al Asad, Iraq.jpg|thumb|A massive [[sand storm]] cloud is about to envelop a military camp as it rolls over [[Al Asad Airbase|Al Asad]], Iraq, just before nightfall on 27 April 2005]]

Wind dominates the transport of sand and finer sediments in arid environments. Wind transport is also important in [[periglacial]] areas, on river [[flood plain]]s, and in coastal areas. Coastal winds transport significant amounts of [[siliciclastic]] and carbonate sediments inland, while wind storms and dust storms can carry clay and silt particles great distances. Wind transports much of the sediments deposited in deep ocean basins.<ref name=Boggs2006/> In ''[[Erg (landform)|ergs]]'' (desert sand seas), wind is very effective at transporting grains of sand size and smaller.{{sfn|Leeder |2011 |p=296}}

Particles are transported by winds through suspension, [[Saltation (geology)|saltation]] (skipping or bouncing) and creeping (rolling or sliding) along the ground. The minimum wind velocity to initiate transport is called the ''fluid threshold'' or ''static threshold'' and is the wind velocity required to begin dislodging grains from the surface. Once transport is initiated, there is a cascade effect from grains tearing loose other grains, so that transport continues until the wind velocity drops below the ''dynamic threshold'' or ''impact threshold'', which is usually less than the fluid threshold. In other words, there is [[hysteresis]] in the wind transport system.<ref name=Boggs2006/><ref>{{cite journal |last1=Raffaele |first1=Lorenzo |last2=Bruno |first2=Luca |last3=Pellerey |first3=Franco |last4=Preziosi |first4=Luigi |title=Windblown sand saltation: A statistical approach to fluid threshold shear velocity |journal=Aeolian Research |date=December 2016 |volume=23 |pages=79–91 |doi=10.1016/j.aeolia.2016.10.002|bibcode=2016AeoRe..23...79R |url=http://porto.polito.it/2662906/ }}</ref>

Small particles may be held in the [[atmosphere]] in suspension. Turbulent air motion supports the weight of suspended particles and allows them to  be transported for great distances. Wind is particularly effective at separating sediment grains under 0.05&nbsp;mm in size from coarser grains as suspended particles.<ref name=Boggs2006/>

Saltation is downwind movement of particles in a series of jumps or skips. Saltation is most important for grains of up to 2&nbsp;mm in size. A saltating grain may hit other grains that jump up to continue the saltation. The grain may also hit larger grains (over 2&nbsp;mm in size) that are too heavy to hop, but that slowly creep forward as they are pushed by saltating grains.<ref name=Boggs2006/> Surface creep accounts for as much as 25 percent of grain movement in a desert.<ref name="ZhengWang2014"/>

Vegetation is effective at suppressing aeolian transport. Vegetation cover of as little as 15% is sufficient to eliminate most sand transport.<ref>{{Cite journal|last1=Lancaster|first1=Nicholas|last2=Baas|first2=Andy|date=1 January 1998|title=Influence of vegetation cover on sand transport by wind: field studies at Owens Lake, California|journal=Earth Surface Processes and Landforms|language=en|volume=23|issue=1|pages=69–82|doi=10.1002/(SICI)1096-9837(199801)23:1<69::AID-ESP823>3.0.CO;2-G|issn=1096-9837|bibcode=1998ESPL...23...69L}}</ref><ref>{{Cite journal|last1=Yan|first1=Yuchun|last2=Xu|first2=Xingliang|last3=Xin|first3=Xiaoping|last4=Yang|first4=Guixia|last5=Wang|first5=Xu|last6=Yan|first6=Ruirui|last7=Chen|first7=Baorui|date=1 December 2011|title=Effect of vegetation coverage on aeolian dust accumulation in a semiarid steppe of northern China|journal=CATENA|volume=87|issue=3|pages=351–356|doi=10.1016/j.catena.2011.07.002|bibcode=2011Caten..87..351Y }}</ref> The size of shore dunes is limited mostly by the amount of open space between vegetated areas.<ref name=Thornbury1969/>

Aeolian transport from deserts plays an important role in ecosystems globally. For example, wind transports minerals from the [[Sahara]] to the [[Amazon basin]].<ref name="KorenKaufman2006">{{cite journal |url=https://www.researchgate.net/publication/230961494 |access-date=14 January 2016 |last1=Koren|first1=Ilan|last2=Kaufman|first2=Yoram J|last3=Washington|first3=Richard|last4=Todd|first4=Martin C|last5=Rudich|first5=Yinon|last6=Martins|first6=J Vanderlei|last7=Rosenfeld|first7=Daniel|title=The Bodélé depression: a single spot in the Sahara that provides most of the mineral dust to the Amazon forest|journal=Environmental Research Letters|volume=1|issue=1|year=2006|pages=014005|issn=1748-9326|doi=10.1088/1748-9326/1/1/014005|bibcode=2006ERL.....1a4005K |doi-access=free}}</ref> Saharan dust is also responsible for forming red clay soils in southern Europe.<ref>{{cite journal|last1=Muhs|first1=Daniel R.|last2=Budahn|first2=James|last3=Avila|first3=Anna|last4=Skipp|first4=Gary|last5=Freeman|first5=Joshua|last6=Patterson|first6=DeAnna|title=The role of African dust in the formation of Quaternary soils on Mallorca, Spain and implications for the genesis of Red Mediterranean soils|journal=Quaternary Science Reviews|date=September 2010|volume=29|issue=19–20|pages=2518–2543|doi=10.1016/j.quascirev.2010.04.013|bibcode=2010QSRv...29.2518M}}</ref>

===Dust storms===
{{Main|Dust storm}}
Dust storms are wind storms that have entrained enough dust to reduce [[visibility]] to less than {{convert|1|km|sigfig=1|sp=us}}.{{sfn|Allaby|2013|loc="dust storm"}}<ref name="Lancaster2014">{{cite journal |last1=Lancaster |first1=N. |title=Aeolian Processes |journal=Reference Module in Earth Systems and Environmental Sciences |date=2014 |pages=B9780124095489091260 |doi=10.1016/B978-0-12-409548-9.09126-0|isbn=9780124095489 }}</ref> Most occur on the [[Synoptic scale meteorology|synoptic]] (regional) scale, due to strong winds along [[weather fronts]],<ref name="RashkiEtal2021">{{cite journal |last1=Rashki |first1=A. |last2=Middleton |first2=N.J. |last3=Goudie |first3=A.S. |title=Dust storms in Iran – Distribution, causes, frequencies and impacts |journal=Aeolian Research |date=January 2021 |volume=48 |pages=100655 |doi=10.1016/j.aeolia.2020.100655|bibcode=2021AeoRe..4800655R |s2cid=229440204 }}</ref> or locally from [[downburst]]s from thunderstorms.<ref>{{cite web |title=What is a dust storm? |url=https://scijinks.gov/dust-storm/ |website=SciJinks |publisher=U.S. National Oceanic and Atmospheric Administration |access-date=10 March 2022}}</ref><ref name="WMO">{{cite web |title=Sand and dust storms |date=8 February 2017 |url=https://public-old.wmo.int/en/our-mandate/focus-areas/environment/sand-and-dust-storms |archive-url=https://web.archive.org/web/20231218181958/https://public-old.wmo.int/en/our-mandate/focus-areas/environment/sand-and-dust-storms |url-status=dead |archive-date=18 December 2023 |publisher=World Meteorological Organization |access-date=10 March 2022}}</ref>

[[Crops]], people, and possibly even [[climate]]s are affected by dust storms. On Earth, dust can cross entire oceans, as occurs with dust from the Sahara that reaches the [[Amazon Basin]].<ref name="WMO"/> Dust storms on [[Mars]] periodically engulf the entire planet.<ref name="Mersmann2015">{{cite web |last1=Mersmann |first1=Kathryn |title=The Fact and Fiction of Martian Dust Storms |url=https://www.nasa.gov/feature/goddard/the-fact-and-fiction-of-martian-dust-storms |publisher=NASA |access-date=11 March 2022 |date=18 September 2015}}</ref> When the [[Mariner 9]] spacecraft entered its orbit around [[Mars]] in 1971, a dust storm lasting one month covered the entire planet, thus delaying the task of photo-mapping the planet's surface.<ref>{{cite web |url=http://lukew.com/marsgeo/aeolian.html |last=Hsui |first=Albert T. |date=2001 |title=Geology of Mars: Aeolian |access-date=30 September 2012}}</ref>

Most of the dust carried by dust storms is in the form of [[silt]]-size particles. Deposits of this windblown silt are known as [[loess]]. The thickest known deposit of loess, up to {{convert|350|m||sp=us}}, is on the [[Loess Plateau]] in [[China]].<ref>{{cite journal |last1=Zhu |first1=Yuanjun |last2=Jia |first2=Xiaoxu |last3=Shao |first3=Mingan |title=Loess Thickness Variations Across the Loess Plateau of China |journal=Surveys in Geophysics |date=July 2018 |volume=39 |issue=4 |pages=715–727 |doi=10.1007/s10712-018-9462-6|bibcode=2018SGeo...39..715Z |s2cid=133922132 }}</ref> This very same Asian dust is blown for thousands of miles, forming deep beds in places as far away as Hawaii.<ref name="KurtzDerry2001">{{cite journal |last1=Kurtz |first1=Andrew C |last2=Derry |first2=Louis A |last3=Chadwick |first3=Oliver A |title=Accretion of Asian dust to Hawaiian soils: isotopic, elemental, and mineral mass balances |url=http://www.geo.cornell.edu/geology/research/derry/publications/Kurtz_dust.pdf |journal=Geochimica et Cosmochimica Acta |volume=65 |issue=12|year=2001 |pages=1971–1983 |access-date=14 January 2016 |issn=0016-7037 |doi=10.1016/S0016-7037(01)00575-0|bibcode=2001GeCoA..65.1971K }}</ref> The [[Peoria Loess]] of North America is up to {{convert|40|m||sp=us}} thick in parts of western [[Iowa]].<ref name="MuhsEtal2014">{{cite book |last1=Muhs |first1=Daniel R. |last2=Cattle |first2=Stephen R. |last3=Crouvi |first3=Onn |last4=Rousseau |first4=Denis-Didier |last5=Sun |first5=Jimin |last6=Zárate |first6=Marcelo A. |chapter=Loess Records |title=Mineral Dust |date=2014 |pages=411–441 |doi=10.1007/978-94-017-8978-3_16|isbn=978-94-017-8977-6 }}</ref> The soils developed on loess are generally highly productive for agriculture.<ref>{{cite book|last=Getis|first=Arthur|author2=Judith Getis and Jerome D. Fellmann|title=Introduction to Geography, Seventh Edition|year=2000|publisher=[[McGraw Hill]]|isbn=0-697-38506-X|page=[https://archive.org/details/introductiontoge00geti/page/99 99]|url=https://archive.org/details/introductiontoge00geti/page/99}}</ref>

Small whirlwinds, called [[dust devil]]s, are common in arid lands and are thought to be related to very intense local heating of the air that results in instabilities of the air mass. Dust devils may be as much as one kilometer high.<ref>{{cite web | publisher=Arizona Vacation Planner | title=Dust Devils: Ephemeral Whirlwinds Can Stir Up Trouble | url=http://www.arizona-vacation-planner.com/dust-devils.html | archive-url=https://archive.today/20120718220124/http://www.arizona-vacation-planner.com/dust-devils.html | url-status=dead | archive-date=18 July 2012 | access-date=5 October 2007}}</ref> Dust devils on Mars have been observed as high as {{convert|10|km||sp=us}}, though this is uncommon.<ref>{{cite journal |last1=Jackson |first1=Brian |title=On the relationship between dust devil radii and heights |journal=Icarus |date=March 2020 |volume=338 |pages=113523 |doi=10.1016/j.icarus.2019.113523|pmid=31806915 |pmc=6894178 |arxiv=1910.14135 |bibcode=2020Icar..33813523J }}</ref>

==Deposition==
[[File:Mesquite Sand Dunes.JPG|thumb|Mesquite Flat Dunes in [[Death Valley]] looking toward the [[Cottonwood Mountains (Inyo County)|Cottonwood Mountains]] from the north west arm of Star Dune (2003)]]
[[File:Aeolian deposition near Addeha.jpg|thumb|Aeolian deposition near Addeha, [[Kola Tembien]], [[Ethiopia]] (2019)]]
{{See also|Aeolian landform}}

Wind is very effective at separating sand from silt and clay. As a result, there are distinct sandy (erg) and silty (loess) aeolian deposits, with only limited [[interbedding]] between the two. Loess deposits are found further from the original source of sediments than ergs. An example of this is the [[Sandhills (Nebraska)|Sand Hills]] of [[Nebraska]], US. Here vegetation-stabilized sand dunes are found to the west and loess deposits to the east, further from the original sediment source in the [[Ogallala Formation]] at the feet of the Rocky Mountains.<ref name=Thornbury1969/>

Some of the most significant experimental measurements on aeolian landforms were performed by [[Ralph Alger Bagnold]],{{sfn|Boggs|2006|p=260}} a British army engineer who worked in [[Egypt]] prior to [[World War II]]. Bagnold investigated the physics of particles moving through the [[atmosphere]] and deposited by wind.<ref name="frs">{{Cite journal | last1 = Kenn | first1 = M. J. | doi = 10.1098/rsbm.1991.0003 | title = Ralph Alger Bagnold. 3 April 1896 – 28 May 1990 | journal = [[Biographical Memoirs of Fellows of the Royal Society]] | volume = 37 | pages = 56–68| year = 1991 | s2cid = 72031353 }}</ref> He recognized two basic dune types, the crescentic dune, which he called "[[barchan]]", and the linear dune, which he called [[Dune#Longitudinal (Seif) and transverse dunes|longitudinal or "seif"]] (Arabic for "sword"). Bagnold developed a classification scheme that included small-scale ripples and sand sheets as well as various types of dunes.<ref name=Thornbury1969/>

Bagnold's classification is most applicable in areas devoid of vegetation.<ref name=Thornbury1969/> In 1941, [[John Tilton Hack]] added parabolic dunes, which are strongly influenced by vegetation, to the list of dune types.<ref>{{cite journal|jstor=210206|title=Dunes of the Western Navajo Country|last1=Hack|first1=John T.|journal=Geographical Review|year=1941|volume=31|issue=2|pages=240–263|doi=10.2307/210206|bibcode=1941GeoRv..31..240H }}
</ref> The discovery of dunes on Mars reinvigorated aeolian process research,{{sfn|Leeder |2011 |p=159}} which increasingly makes use of computer simulation.{{sfn|Boggs|2006|p=260}}

Wind-deposited materials hold clues to past as well as to present wind directions and intensities. These features help us understand the present climate and the forces that molded it.<ref name=Thornbury1969/> For example, vast inactive ergs in much of the modern world attest to late Pleistocene trade wind belts being much expanded during the Last Glacial Maximum. Ice cores show a tenfold increase in non-volcanic dust during glacial maxima. The highest dust peak in the Vostok [[ice core]]s dates to 20 to 21 thousand years ago. The abundant dust is attributed to a vigorous low-latitude wind system plus more exposed continental shelf due to low sea levels.{{sfn|Leeder |2011 |p=297}}

Wind-deposited sand bodies occur as [[Ripple marks|ripples]] and other small-scale features, [[sand sheet]]s, and [[dune]]s.

===Ripples and other small-scale features===
[[File:1969 Afghanistan (Sistan) wind ripples.tiff|thumb|upright|Wind ripples on crescent-shaped sand dunes (barchans) in southwest [[Afghanistan]] ([[Sistan]])]]
Wind blowing on a sand surface [[ripple (fluid dynamics)|ripples]] the surface into [[crest (physics)|crest]]s and troughs whose long axes are [[perpendicular]] to the wind direction. The average length of jumps during saltation corresponds to the [[wavelength]], or distance between adjacent crests, of the ripples. In ripples, the coarsest materials collect at the crests causing [[graded bedding|inverse grading]]. This distinguishes small ripples from dunes, where the coarsest materials are generally in the troughs. This is also a distinguishing feature between water laid ripples and aeolian ripples.{{sfn|Leeder|2011|pp=155–161}}

A ''sand shadow'' is an accumulation of sand on the downwind side of an obstruction, such as a boulder or an isolated patch of vegetation. Here the sand builds up to the [[angle of repose]] (the maximum stable slope angle), about 34 degrees, then begins sliding down the ''slip face'' of the patch. A ''sandfall'' is a sand shadow of a cliff or escarpment.<ref name=Thornbury1969/>

Closely related to sand shadows are ''sand drifts''. These form downwind of a gap between obstructions, due to the funneling effect of the obstructions on the wind.<ref name=Thornbury1969/>

===Sand sheets===
{{Main|Sand sheet}}
Sand sheets are flat or gently undulating sandy deposits with only small surface ripples. An example is the Selima Sand Sheet in the eastern Sahara Desert, which occupies {{convert|60000|km2||sp=us}} in southern [[Egypt]] and northern [[Sudan]]. This consists of a few feet of sand resting on bedrock. Sand sheets are often remarkably flat and are sometimes described as ''desert peneplains''.<ref name=Thornbury1969/>

Sand sheets are common in desert environments, particularly on the margins of dune fields, although they also occur within ergs.  Conditions that favor the formation of sand sheets, instead of dunes, may include surface cementation, a high water table, the effects of vegetation, periodic flooding, or sediments rich in grains too coarse for effective saltation.<ref>{{cite journal |last1=Kocurek |first1=Gary |last2=Nielson |first2=Jamie |title=Conditions favourable for the formation of warm-climate aeolian sand sheets |journal=Sedimentology |date=December 1986 |volume=33 |issue=6 |pages=795–816 |doi=10.1111/j.1365-3091.1986.tb00983.x|bibcode=1986Sedim..33..795K }}</ref>

===Dunes===
[[File:Rub al Khali 002.JPG|thumb|Sand dunes of the [[Empty Quarter]] to the east of [[Liwa Oasis]], United Arab Emirates]]
{{Main|Dune}}
A dune is an accumulations of sediment blown by the wind into a [[mound]] or [[ridge]]. They differ from sand shadows or sand drifts in that they are independent of any topographic obstacle.<ref name=Thornbury1969/> Dunes have gentle upwind slopes on the [[windward]] side. The downwind portion of the dune, the lee slope, is commonly a steep [[avalanche]] slope referred to as a [[slipface]]. Dunes may have more than one slipface. The minimum height of a slipface is about 30 centimeters.{{sfn|Boggs|2006|pp=260–263}}

Wind-blown sand moves up the gentle upwind side of the dune by saltation or creep. Sand accumulates at the brink, the top of the slipface. When the buildup of sand at the brink exceeds the [[angle of repose]], a small [[avalanche]] of grains slides down the slipface. Grain by grain, the dune moves downwind.{{sfn|Boggs|2006|pp=260–263}}

Dunes take three general forms. Linear dunes, also called longitudinal dunes or seifs, are aligned in the direction of the prevailing winds. Transverse dunes, which include crescent dunes (barchans), are aligned perpendicular to the prevailing winds. More complex dunes, such as star dunes, form where the directions of the winds are highly variable.  Additional dune types arise from various kinds of topographic forcing, such as from isolated hills or escarpments.{{sfn|Leeder|2011|p=162}}

====Transverse dunes====
[[File:Mesquite Sand Dunes.JPG|thumb|Typical shape]]
Transverse dunes occur in areas dominated by a single direction of the prevailing wind. In areas where sand is not abundant, transverse dunes take the form of barchans or crescent dunes. These are not common, but they are highly recognizable, with a distinctive crescent shape with the tips of the crescent directed downwind. The dunes are widely separated by areas of bedrock or reg. Barchans migrate up to {{convert|30|m||sp=us}} per year, with the taller dunes migrating faster. Barchans first form when some minor topographic feature creates a sand patch. This grows into a sand mound, and the converging streamlines of the air flow around the mound build it into the distinctive crescent shape. Growth is ultimately limited by the carrying capacity of the wind, which as the wind becomes saturated with sediments, builds up the slip face of the dune.  Because barchans develop in areas of limited sand availability, they are poorly preserved in the geologic record.{{sfn|Leeder|2011|p=163}}

Where sand is more abundant, transverse dunes take the form of aklé dunes, such as those of the western Sahara. These form a network of sinuous ridges perpendicular to the wind direction.{{sfn|Jackson|1997|loc="aklé}} Aklé dunes are preserved in the geologic record as sandstone with large sets of [[cross-bedding]] and many reactivation surfaces.{{sfn|Leeder|2011|p=163}}

[[Draa (landform)|Draas]] are very large composite transverse dunes. They can be up to {{convert|4000|m||sp=us}} across and {{convert|400|m||sp=us}} high and extend lengthwise for hundreds of kilometers. In form, they resemble a large aklé or barchanoid dune. They form over a prolonged period of time in areas of abundant sand and show a complex internal structure. Careful 3-D mapping is required to determine the morphology of a draa preserved in the geologic record.{{sfn|Leeder|2011|p=164}}

====Linear dunes====
[[File:Rub' al Khali (Arabian Empty Quarter) sand dunes imaged by Terra (EOS AM-1).jpg|thumb|Rub' al Khali (Arabian Empty Quarter) sand dunes imaged by Terra (EOS AM-1). Most of these dunes are seif dunes. Their origin from barchans is suggested by the stubby remnant "hooks" seen on many of the dunes. Wind would be from left to right.]]
Linear dunes can be traced up to tens of kilometers, with heights sometimes in excess of {{convert|70|m||sp=us}}. They are typically several hundred meters across and are spaced {{convert|1 to 2|km||sp=us}}apart. They sometimes coalesce at a Y-junction with the fork directed upwind. They have a sharp sinuous or en echelon crest. They are thought to form from a bimodal seasonal wind pattern, with a weak wind season characterized by wind directed an at acute angle to the prevailing winds of the strong wind season. The strong wind season produces a barchan form and the weak wind season stretches this into the linear form. Another possibility is that these dunes result from [[secondary flow]], though the precise mechanism remains uncertain.{{sfn|Leeder|2011|pp=164–167}}

====Complex dunes====
Complex dunes (star dunes or rhourd dunes) are characterized by having more than two slip faces. They are typically {{convert|500 to 1000|m||sp=us}} across and {{convert|50 to 300|m||sp=us}} high. They consist of a central peak with radiating crests and are thought to form where strong winds can come from any direction. Those in [[Gran Desierto de Altar]] of Mexico are thought to have formed from precursor linear dunes due to a change in the wind pattern about 3000 years ago. Complex dunes show Little lateral growth but strong vertical growth and are important sand sinks.{{sfn|Leeder|2011|pp=167–168}}

====Other dune types====
Vegetated parabolic dunes are crescent-shaped, but the ends of the crescent point upwind, not downwind. They form from the interaction of vegetation patches with active sand sources, such as blowouts. The vegetation stabilizes the arms of the dune, and an elongated lake sometimes forms between the arms of the dune.{{sfn|Leeder|2011|pp=168–169}}

Clay dunes are uncommon but have been found in Africa, Australia, and along the Gulf Coast of North America.<ref name=Thornbury1969/> These form on mud flats on the margins of saline bodies of water subject to strong prevailing winds during a dry season. Clay particles are bound into sand-sized pellets by salts and are then deposited in the dunes, where the return of the cool season allows the pellets to absorb moisture and become bound to the dune surface.<ref>{{cite journal |last1=Bowler |first1=J.M. |title=Clay Dunes: Their occurrence, formation and environmental significance |journal=Earth-Science Reviews |date=December 1973 |volume=9 |issue=4 |pages=315–338 |doi=10.1016/0012-8252(73)90001-9|bibcode=1973ESRv....9..315B }}</ref>

==Aeolian desert systems==
[[File:Sahara satellite hires.jpg|thumb|Satellite image of Sahara]]
[[File:Unsettled Weather Across Central Australia.jpg|thumb|Unsettled Weather system moving across the Australian desert]]
[[File:Loess landscape china.jpg|thumb|[[Loess Plateau]] near [[Hunyuan County|Hunyuan, Shanxi]]]]
[[Deserts]] cover 20 to 25 percent of the modern land surface of the earth, mostly between the latitudes of 10 to 30 degrees north or south. Here the descending part of the tropical atmospheric circulation (the [[Hadley cell]]) produces high atmospheric pressure and suppresses precipitation. Large areas of this desert is floored with windblown sand. Such areas are called ''[[Erg (landform)|ergs]]'' when they exceed about {{convert|125|km2||sp=us}} in area or ''dune fields'' when smaller. Ergs and dune fields make up about 20% of modern deserts or about 6% of the Earth's total land surface.{{sfn|Boggs|2006|p=258}}

The sandy areas of today's world are somewhat anomalous. Deserts, in both the present day and in the geological record, are usually dominated by [[alluvial fan]]s rather than dune fields. The present relative abundance of sandy areas may reflect reworking of [[Tertiary]] sediments following the Last Glacial Maximum.<ref name=BlattEtal1980>{{cite book |last1=Blatt |first1=Harvey |last2=Middleton |first2=Gerard |last3=Murray |first3=Raymond |title=Origin of sedimentary rocks |date=1980 |publisher=Prentice-Hall |location=Englewood Cliffs, N.J. |isbn=0136427103 |edition=2nd |pages=642–646}}</ref> Most modern deserts have experienced extreme [[Quaternary]] climate change, and the sediments that are now being churned by wind systems were generated in upland areas during previous [[pluvial]] (moist) periods and transported to depositional basins by stream flow. The sediments, already [[Sorting (sediment)|sorted]] during their initial fluvial transport, were further sorted by wind, which also sculpted the sediments into eolian landforms.<ref name=Leeder2011/>

The state of an aeolian system depends mainly on three things: The amount of sediment supply, the availability of sediments, and the transport capacity of the winds. The sediment supply is largely produced in [[pluvial]] periods (periods of greater rainfall) and accumulates by runoff as [[Alluvial fan|fan deltas or terminal fans]] in [[sedimentary basin]]s. Another important source of sediments is the reworking of [[Carbonate rock|carbonate]] sediments on [[continental shelves]] exposed during times of lower sea level. Sediment availability depends on the coarseness of the local sediment supply, the degree of exposure of sediment grains, the amount of soil moisture, and the extent of vegetation coverage. The potential transport rate of wind is usually more than the actual transport, because the sediment supply is usually insufficient to saturate the wind. In other words, most aeolian systems are ''transport-undersaturated'' (or ''sediment-undersaturated'').{{sfn|Leeder|2011|pp=297, 162–163}}

Aeolian desert systems can be divided into wet, dry, or stabilized systems. Dry systems have the [[water table]] well below the  surface, where it has no stabilizing effect on sediments. Dune shapes determine whether sediment is deposited, simply moves across surface (a ''bypass'' system), or erosion takes place. Wet systems are characterized by a water table near the depositional surface, which exerts a strong control on deposition, bypass, or erosion. Stabilized systems have significant vegetation, surface cement, or mud drapes which dominate the evolution of the system. The Sahara shows the full range of all three types.{{sfn|Boggs|2006|pp=263–268}}

The movement of sediments in aeolian systems can be represented by sand-flow maps. These are based on meteorological observations, bedform orientations, and trends of yardangs. They are analogous to drainage maps, but are not as closely tied to topography, since wind can blow sand significant distances uphill.{{sfn|Leeder|2011|p=297}}

The Sahara of North Africa is the largest hot desert in the world.<ref>{{cite journal|last1=Cook|first1=Kerry H.|last2=Vizy|first2=Edward K.|title=Detection and Analysis of an Amplified Warming of the Sahara Desert|journal=Journal of Climate|date=2015|volume=28|issue=16|page=6560|doi=10.1175/JCLI-D-14-00230.1|bibcode=2015JCli...28.6560C|doi-access=free}}</ref> Flowlines can be traced from erg to erg, demonstrating very long transport downwind. Satellite observations show yardangs aligned with the sandflow lines. All flowlines arise in the desert itself, and show indications of clockwise circulation roughly like [[High-pressure area|high pressure cells]]. The greatest deflation occurs in dried lake beds where trade winds form a low-level jet between the [[Tibesti Mountains]] and the [[Ennedi Plateau]]. The flowlines eventually reach the, sea creating great plume of Saharan dust extending thousands of kilometers into the Atlantic Ocean. This creates a steady rain of silt into the ocean. It is estimated that 260 million tons of sediments are transported through this system each year, but the amount was much greater during the [[Last Glacial Maximum]], based on deep-sea cores. Mineral dust of 0.1–1 microns in size is a good shortwave radiation scatterer and has a cooling effect on climate.{{sfn|Leeder|2011|pp=299–301}}

Another example of an aeolian system is the arid interior of Australia. With few topographic barriers to sand  movement, an anticlockwise wind system is traced by systems of longitudinal dunes.{{sfn|Leeder|2011|p=301}}

The [[Namib]] and [[Oman]] ergs are fed by coastal sediments. The Namib receives its sediments from the south through narrow deflation corridors from coast that cross more than {{convert|100|km||sp=us}} of bedrock to the erg. The Oman was created by deflation of marine shelf carbonates during the last Pleistocene lowstand of the sea.{{sfn|Leeder |2011 |p=297}}

The [[Loess Plateau]] of China has been a long-term sink for sediments during the Quaternary ice age. It provides a record of glaciation, in the form of glacial loess layers separated by [[paleosol]]s (fossil soils). The loess layers were desposited by a strong northwest winter monsoon, while the paleosols record the influence of a moist southeast monsoon.{{sfn|Leeder |2011 |p=297}}

The African [[savannah]] is mostly ergs deposited during the Last Glacial Maximum that are now stabilized by vegetation.{{sfn|Leeder |2011 |p=297}}

===Examples===
Major global aeolian systems thought to be linked with weather and climate variation:

* An average of 132 million tons of dust from the [[Sahara]] (primarily the [[Sahel]] and [[Bodélé Depression]]) across the Atlantic each year.<ref>{{Cite web | url=https://www.nasa.gov/content/goddard/nasa-satellite-reveals-how-much-saharan-dust-feeds-amazon-s-plants | title=Saharan Dust Feeds Amazon's Plants| date=24 February 2015}}</ref> 
* [[Harmattan]] winter dust storms in [[West Africa]] also occur blowing dust to the ocean.{{sfn|Allaby|2013|loc="harmattan wind (the doctor)"}}
* [[Asian dust]] originates in the [[Gobi Desert]] and reaches Korea, Japan, Taiwan (at times) and even the western US.<ref name="News">{{cite web|url=http://www.sciencenews.org/articles/20011006/bob13.asp |title=Ill Winds |work=Science News Online |access-date=6 October 2001 |url-status=dead |archive-url=https://web.archive.org/web/20040319153009/http://www.sciencenews.org/articles/20011006/bob13.asp |archive-date=19 March 2004 }}</ref>
* The [[2018 Indian dust storms]] transported dust from the [[Thar Desert]] towards Delhi, Uttar Pradesh, and the [[Indo-Gangetic Plain]].
* [[Shamal (wind)|Shamal]] June–July winds blowing dust in primarily north to south in Saudi Arabia, Iran, Iraq, UAE, and parts of Pakistan.
* [[Haboob]] dust storms in Sudan, Australia, Arizona associated with [[monsoon]].
* [[Khamsin]] dust from Libya, Egypt and Levant in Spring associated with [[extratropical cyclones]].
* [[Dust Bowl]] event in US, carried sand eastward.  5500 tons were deposited in Chicago area.
* [[Sirocco]] sandy winds from Africa/Sahara blowing north into South Europe.
* [[Kalahari Desert]] blowing sand/dust east across southern Africa toward Indian Ocean.
* [[Mars]] in the arid conditions, many aeolian processes have been discovered.<ref>{{cite journal |last1=Chojnacki |first1=Matthew |title=Persistent aeolian activity at Endeavour crater, Meridiani Planum, Mars; new observations from orbit and the surface |journal=  Icarus|date=1 May 2015 |volume=251 |pages=275–290 |doi=10.1016/j.icarus.2014.04.044 |bibcode=2015Icar..251..275C |url=https://www.sciencedirect.com/science/article/abs/pii/S001910351400236X |access-date=19 October 2021|url-access=subscription }}</ref>

===In the geologic record===
[[Image:Cross-bedding Of Sandstone Near Mt Carmel Road Zion Canyon Utah.jpg|thumb|300px|right|Cross-bedding of [[sandstone]] near Mt. Carmel road, [[Zion National Park|Zion Canyon]]]]
Aeolian processes can be discerned at work in the geologic record as long ago as the [[Precambrian]]. Aeolian [[Geological formation|formations]] are prominent in the [[Paleozoic]] and [[Mesozoic]] of the western US. Other examples include the [[Permian]] [[Rotliegendes]] of northwestern Europe; the [[Jurassic]]–[[Cretaceous]] [[Botucatu Formation]] of the [[Parana Basin]] of Brazil; the Permian [[Lower Bunter Sandstone]] of Britain; the Permian-[[Triassic]] [[Corrie Sandstone]] and [[Hopeman Sandstone]] of Scotland; and the [[Proterozoic]] sandstones of India and northwest Africa.{{sfn|Boggs|2006|pp=263–268}}

Perhaps the best examples of aeolian processes in the geologic record are the Jurassic ergs of the western US. These include the [[Wingate Sandstone]], the [[Navajo Sandstone]], and the [[Page Sandstone]]. Individual formations are separated by regional [[Unconformity|unconformities]] indicate erg stabilization. The ergs interfingered with adjacent river systems, as with the Wingate Sandstone interfingering with the [[Moenave Formation]] and the Navajo Sandstone with the [[Kayenta Formation]].{{sfn|Leeder|2011|p=314}}

The Navajo and [[Nugget Sandstone]]s were part of the largest erg deposit in the geologic record. These formations are up to {{convert|700|m||sp=us}} thick and are exposed over {{convert|265000|km2||sp=us}}. Their original extent was likely 2.5 times the present outcrop area. Though once thought to possibly be marine in origin, they are now all but universally regarded as aeolian deposits. They are made up mostly of fine- to medium-sized quartz grains that are well-rounded and frosted, both indications of aeolian transport. The Navajo contains huge tabular crossbed sets with sweeping foresets. Individual crossbed sets dip at an angle of more than 20 degrees and are from {{convert|5 to 35|m||sp=us}} thick. The formation contains freshwater invertebrate fossils and vertebrate tracks. Slump structures (contorted bedding) are present that resemble those in modern wetted dunes. Successive migrating dunes deposited a vertical stacking of eolian beds between interdune bounding surfaces and regional supersurfaces.{{sfn|Boggs|2006|pp=263–268}}

The Permian [[Rotliegend Group]] of the North Sea and north Europe contains sediments from adjacent uplands. Erg sand bodies within the group are up to {{convert|500|m||sp=us}} thick. Study of the crossbedding shows that sediments were deposited by a clockwise atmospheric cell. Drilling core show dry and wet interdune surfaces and regional supersurfaces, and provide evidence of five or more cycles of erg expansion and contraction. A global rise in sea level finally drowned the erg and deposited the beds of the [[Weissliegend]].{{sfn|Leeder|2011|p=312}}

The [[Cedar Mesa Sandstone]] in Utah was contemporary with the Rogliegend. This formation records at least 12 erg sequences bounded by regional deflation supersurfaces. Aeolian landforms preserved in the formation range from damp sandsheet and lake [[paleosol]] (fossil soil) beds to thin, chaotically arranged dune sets to equilibrium erg construction, with dunes {{convert|300 to 400|m||sp=us}} wide migrating over still larger draas. The draas survived individual climate cycles, and their interdunes were sites of barchan nucleation during arid portions of the climate cycles.{{sfn|Leeder|2011|p=314}}

{{clear}}

==See also==
{{Div col}}
*{{annotated link|Bagnold formula}}
*{{annotated link|Bibliography of Aeolian Research|''Bibliography of Aeolian Research''}}
*{{annotated link|Dreikanter}}
*{{annotated link|Médanos (geology)}}
*{{annotated link|Niveo-aeolian deposition}}
*{{annotated link|Sandhill}}
*{{annotated link|The Physics of Blown Sand and Desert Dunes|''The Physics of Blown Sand and Desert Dunes''}}
*{{annotated link|Wind Erosion on European Light Soils}}
{{div col end}}

==References==
{{Reflist}}

==Further reading==
* {{Cite book |last=Hughes |first=J. Donald |year=2016 |title=What Is Environmental History? |edition= 2nd. |location=Cambridge |publisher=Polity Press}}

==External links==
*{{URL|https://data.mendeley.com/datasets/675gwk5jp7/1|The Bibliography of Aeolian Research}}
*[https://digital.library.unt.edu/permalink/meta-dc-1551:1 ''Facts about wind erosion and dust storms on the Great Plains''], hosted by the [https://digital.library.unt.edu/browse/department/govdocs/ UNT Government Documents Department]
*[http://www.sciencedirect.com/science/journal/18759637 ''Aeolian Research'']
*[http://www.aeolianresearch.org International Society for Aeolian Research, ISAR] {{Webarchive|url=https://web.archive.org/web/20170912131124/http://www.aeolianresearch.org/ |date=12 September 2017 }}
*{{cite web | title = Eolian Processes | publisher = USGS | year = 1997 | url = http://pubs.usgs.gov/gip/deserts/eolian/ | access-date = 1 November 2006| archive-url= https://web.archive.org/web/20061201140005/http://pubs.usgs.gov/gip/deserts/eolian/| archive-date= 1 December 2006 | url-status= live}}
*{{URL|https://hirise.lpl.arizona.edu/sim/images/persistent-aeolian-3-large.gif|Persistent aeolian activity on Mars}}

{{Geologic Principles}}
{{Authority control}}

{{DEFAULTSORT:Aeolian Processes}}
[[Category:Aeolian landforms| Aeolian processes]]
[[Category:Deserts]]
[[Category:Geological processes]]
[[Category:Geomorphology]]
[[Category:Pedology]]
[[Category:Sedimentology]]
[[Category:Soil erosion]]