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A ventifact (also wind-faceted stone, windkanter) is a rock that has been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals. These geomorphic features are most typically found in arid environments where there is little vegetation to interfere with
aeolian Aeolian commonly refers to things related to either of two Greek mythological figures: * Aeolus (son of Hippotes), ruler of the winds * Aeolus (son of Hellen), son of Hellen and eponym of the Aeolians * Aeolians, an ancient Greek tribe thought to ...
particle transport, where there are frequently strong winds, and where there is a steady but not overwhelming supply of sand. Ventifacts can be abraded to eye-catching natural sculptures such as the main features of the White Desert National Park near Farafra oasis in Egypt. In moderately tall, isolated rock outcrops, mushroom shaped pillars of rock may form as the outcrop is eroded by 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). 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 striations cut in 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.NASA
Premature Wear of the MSL Wheels
2017-09-26
An example of a Martian ventifact was named Jake Matijevic. By analyzing its shape, it was possible to reconstruct the main wind direction which sculpted the rock.Patrick Zasada (2013) ''Entstehung des Mars-Gesteins "Jake Matijevic"''
Sternzeitissue 2/2013
pp. 98–101. (German language).
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 Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert. During summer, it is the hottest place on Earth. Death Valley's Badwater Basin is the point of lowest elevation in North Am ...
(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 Province, Chile (Segerstrom, 1962) file:Yardang Lea-Yoakum Dunes.jpg, Wind-carved,
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...
yardang in a
blowout Blowout or Blow out may refer to: Film and television *''Blow Out'', a 1981 film by Brian De Palma * ''The Blow Out'', a 1936 short film * ''Blow Out'' (TV series), a TV series on Bravo * "Blow Out" (''Prison Break''), an episode of ''Prison ...
near
Meadow, Texas Meadow is a town in Terry County, Texas, United States. The population was 593 at the 2010 census. Geography Meadow is located at (33.338336, –102.207772). According to the United States Census Bureau, the town has a total area of 1.6 s ...
(Stout, 2002) file:Im Salar de Uyuni.jpg, Rock sculpted into a mushroom-like form by wind
erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is di ...
in the
Altiplano The Altiplano (Spanish for "high plain"), Collao ( Quechua and Aymara: Qullaw, meaning "place of the Qulla") or Andean Plateau, in west-central South America, is the most extensive high plateau on Earth outside Tibet. The plateau is located a ...
region of
Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...
(Wilken, 2002)


See also

* * * * *, Antarctica


References


External links

* {{Authority control Aeolian landforms Petrology Rocks