Ventifact

Aventifact(alsowind-faceted stone,windkanter) is arockthat has been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals.The word “Ventifact” is derived from theLatinword “Ventus” meaning ‘wind’. These geomorphic features are most typically found in arid environments where there is littlevegetationto interfere withaeolianparticle transport, where there are frequently strongwinds,and where there is a steady but not overwhelming supply ofsand.

Wind-carved "mushroom"shaped rocks are the centerpiece ofWhite Desert National Park,Egypt

Ventifacts can be abraded (abrasion) to eye-catching natural sculptures such as the main features of theWhite Desert National ParknearFarafra OasisinEgypt.In moderately tall, isolated rock outcrops,mushroomshaped pillars ofrockmay form as the outcrop is eroded bysaltatingsand grains. This occurs because, even in strongwinds,sandgrains can't be continuously held in theair.Instead, theparticlesbounce along the ground, rarely reaching higher than a few feet above theEarth.Over time, the bouncingsandgrains can erode the lower portions of a ventifact, while leaving a larger less eroded cap. The resulting forms thus frequently resemble fantasticalstonemushrooms.

Individual stones, such as those formingdesert pavement,are often found with grooved, etched, or polishedsurfaceswhere these same wind-driven processes have slowly worn away therock.

Ventifacts are typically of three types - •Einkantershaving one polished side (excluding the bottom part) (Germanword ‘ein’ means ‘one’) •Zweinkantershaving two polished sides (excluding the bottom part)(Germanword ‘zwei’ means ‘two’) •Dreinkantershaving three polished surface (excluding the polished surface at bottom) those meet up at sharp angles(Germanword ‘drei’ means ‘three’)

When ancient ventifacts are preserved without being moved or disturbed, they may serve as a paleo-windindicators. The wind direction at the time the ventifact formed will be parallel to grooves orstriationscut into therock.

Ventifacts have also been discovered onMars,where such sharp immobilerockshave caused significant damage to the wheels of theCuriosityrover.An example of aMartianventifact was namedJake Matijevic.By analyzing its shape, it was possible to reconstruct the mainwinddirection which sculpted therock.

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  Schistboulder pitted by sand blast near Palm Springs Station,Colorado Desert.Riverside County,California(Mendenhall, 1905)
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  Ventifact from theMojave DesertnearBarstow,California.
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  Ventifact at Ventifact Ridge inDeath Valley(Mayer, 2003)
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  Granitedreikanter polished by windblown sand,Sweetwater County,Wyoming (Bradley,1930)
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  Outcrop ofgranitethat has been undercut by the abrasive action of windblown sand, Llano deCaldera,AtacamaProvince,Chile(Segerstrom, 1962)
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  Wind-carved,sandstoneyardangin ablowoutnearMeadow, Texas(Stout, 2002)
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  Rock sculpted into a mushroom-like form by winderosionin theAltiplanoregion ofBolivia(Wilken, 2002)

See also

• Arkenu structures– pair of geological features in LibyaPages displaying wikidata descriptions as a fallback
• Blowout (geomorphology)– Depressions in a sand dune ecosystem caused by the removal of sediments by wind
• Dune– Hill of loose sand built by aeolian processes or the flow of water
• Yardang– Streamlined aeolian landform
• Ventifact Knobs– Geographic feature in AntarcticaPages displaying short descriptions of redirect targets,Antarctica

External links

• The Bibliography of Aeolian Research