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((short description|Rock that has been eroded by wind-driven sand or ice crystals))
((refimprove|date = April 2019))
A '''ventifact''' (also '''wind-faceted stone''', '''windkanter'''<ref>Klaus K. E. Neuendorf, ''Glossary of Geology'', [https://books.google.com/books?id=yD79FqfECCYC&pg=PA723 p. 723]</ref>) is a [[rock (geology)|rock]] that has been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals.<ref>((cite book|first=Julie E. |last=Laity |chapter=19. Landforms, landscapes, and processes of aeolian erosion |editor-last=Parsons|editor-first=Anthony J.|title=Geomorphology of desert environments|date=2009|publisher=Springer|location=[Dordrecht]|isbn=978-1402057199|pages=597–628|edition=2nd.|editor2-last=Abrahams |editor2-first=Athol D.))</ref> These geomorphic features are most typically found in arid environments where there is little vegetation to interfere with [[aeolian processes|aeolian]] particle transport, where there are frequently strong winds, and where there is a steady but not overwhelming supply of sand.

[[File:Weisse Wüste.jpg|thumb|right|Wind-carved "mushroom" rocks are the centerpiece of [[White Desert National Park]], Egypt]]
Ventifacts can be abraded to eye-catching natural sculptures such as the main features of the [[White Desert National Park]] near [[Farafra Oasis|Farafra oasis]] in Egypt. In moderately tall, isolated rock outcrops, mushroom shaped pillars of rock may form as the outcrop is eroded by [[Saltation (geology)|saltating]] sand grains. This occurs because, even in strong winds, sand grains can't be continuously held in the air. Instead, the particles bounce along the ground, rarely reaching higher than a few feet above the Earth. Over time, the bouncing sand grains can erode the lower portions of a ventifact, while leaving a larger less eroded cap. The resulting forms thus frequently resemble fantastical stone mushrooms.

Individual stones, such as those forming [[desert pavement]], are often found with grooved, etched, or polished surfaces where these same wind-driven processes have slowly worn away the rock.

Stones with a small number of wind facets have names reflecting this number, e.g. a  [[dreikanter]] is a roughly pyramidal stone having 3 wind facets (and one buried, rounded side).<ref>((Cite book |last=Livingstone |first=Ian |title=Aeolian geomorphology: an introduction |last2=Warren |first2=Andrew |date=1996 |publisher=Longman |isbn=978-0-582-08704-0 |location=Harlow))</ref>

When ancient ventifacts are preserved without being moved or disturbed, they may serve as a paleo-wind indicators. The wind direction at the time the ventifact formed will be parallel to grooves or [[Striation (geology)|striations]] cut into the rock. 

Ventifacts have also been discovered on Mars, where such sharp immobile rocks have caused significant damage to the wheels of the [[Curiosity (rover)|''Curiosity'' rover]].<ref name=llis>NASA, [https://llis.nasa.gov/lesson/22401 Premature Wear of the MSL Wheels], 2017-09-26</ref> An example of a [[Mars|Martian]] ventifact was named [[Jake Matijevic (rock)|Jake Matijevic]]. By analyzing its shape, it was possible to reconstruct the main wind direction which sculpted the rock.<ref name="PZ13">Patrick Zasada (2013) ''Entstehung des Mars-Gesteins "Jake Matijevic"''. [http://www.sternzeit-online.de/ Sternzeit], [http://www.sternzeit-online.de/?p=archiv&q=2%2F2013 issue 2/2013]: pp. 98–101. (German language).</ref>

<gallery widths=200px>
file:Mendenhall 1905 USGS.jpg|Schist boulder pitted by sand blast near Palm Springs Station, Colorado Desert. Riverside County, California (Mendenhall, 1905)
file:VentifactMojaveDesert031511.jpg|Ventifact from the Mojave Desert near Barstow, California.
file:Ventifact_at_Ventifact_Ridge_in_Death_Valley.jpg|Ventifact at Ventifact Ridge in [[Death Valley]] (Mayer, 2003)
file:Bradley_1930_dreikanter.jpg|Granite [[dreikanter]] polished by windblown sand, Sweetwater County, Wyoming (Bradley, 1930)
file:Segerstrom_1962_USGSProPaper450C.jpg|Outcrop of granite that has been undercut by the abrasive action of windblown sand, Llano de Caldera, [[Atacama Desert|Atacama]] Province, Chile (Segerstrom, 1962)
file:Yardang Lea-Yoakum Dunes.jpg|Wind-carved, [[sandstone]] [[yardang]] in a [[Blowout (geology)|blowout]] near [[Meadow, Texas]] (Stout, 2002)
file:Im Salar de Uyuni.jpg|Rock sculpted into a mushroom-like form by wind [[erosion]] in the [[Altiplano]] region of [[Bolivia]] (Wilken, 2002)
</gallery>

==See also==
*((annotated link|Arkenu structures))
*((annotated link|Blowout (geomorphology)))
*((annotated link|Dune))
*((annotated link|Yardang))
*((annotated link|Ventifact Knobs)), Antarctica

== References ==
((reflist))

==External links==
((commonscat|Ventifact))
*((URL|https://data.mendeley.com/datasets/675gwk5jp7/1|The Bibliography of Aeolian Research))

((Authority control))

[[Category:Aeolian landforms]]
[[Category:Petrology]]
[[Category:Rocks]]

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Arkenu structures (edit)
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Dune (edit)
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Ventifact (edit)
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