Ventifact

Ventifact


U.S. Geological Survey Photographic Library ( http://libraryphoto.cr.usgs.gov/ )]
Atacama Province, Chile (Segerstrom, 1962) [Segerstrom, K. 1962. Deflated marine terrace as a source of dune chains, Atacama Province, Chile. In: Geological Survey research 1962; Short papers in geology and hydrology. United States Department of the Interior, U.S. Geological Survey, Professional Paper 0450-C, pp. 91-93.]
Death Valley (Mayer, 2003)
Ventifacts are rocks that have been abraded, pitted, etched, grooved, or polished by wind-driven sand. These geomorphic features are most typically found in arid environments where there is little vegetation to interfere with aeolian 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. 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 results can be fantastic 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.

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.


U.S. Geological Survey Photographic Library ( http://libraryphoto.cr.usgs.gov/ )]
Atacama Province, Chile (Segerstrom, 1962)
sandstone in a blowout near Meadow, Texas (Stout, 2002)
erosion in the Altiplano region of Bolivia (Wilken, 2002)

References

ee also

*Dreikanter
*Yardang
*Saltation
*Dune
*Blowouts

External links

* [http://www.lbk.ars.usda.gov/wewc/biblio/bar.htm The Bibliography of Aeolian Research]


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Look at other dictionaries:

  • ventifact — [ven′tə fakt΄] n. [< L ventus, a WIND2 + (ART)IFACT] any stone shaped by the abrasion of windblown sand …   English World dictionary

  • ventifact — /ven teuh fakt /, n. Geol. a pebble or cobble that has been faceted, grooved, and polished by the erosive action of wind driven sand. [1910 15; < L venti (comb. form of ventus WIND1) + factum something made (see FACT); perh. modeled on ARTIFACT]… …   Universalium

  • ventifact — noun Etymology: Latin ventus + English artifact Date: 1911 a stone worn, polished, or faceted by windblown sand …   New Collegiate Dictionary

  • ventifact — noun A pebble or little stone shaped and polished by wind blown sand …   Wiktionary

  • ventifact —    A stone or pebble that has been shaped, worn, faceted, cut, or polished by the abrasive action of windblown sand, usually under arid conditions. When the pebble is at the ground surface, as in a desert pavement, the upper part is polished… …   Glossary of landform and geologic terms

  • ventifact — n. rillstone, stone whose surface has been worn down by erosion caused by wind driven sand (Geology) …   English contemporary dictionary

  • ventifact — [ vɛntɪfakt] noun Geology a stone shaped by the erosive action of wind blown sand. Origin early 20th cent.: from L. ventus wind + fact , facere make …   English new terms dictionary

  • ventifact — ven·ti·fact …   English syllables

  • ventifact — ven•ti•fact [[t]ˈvɛn təˌfækt[/t]] n. gel a pebble or cobble that has been faceted, grooved, and polished by the erosive action of wind driven sand • Etymology: 1911; < L venti , comb. form of ventus wind I+(arti)fact …   From formal English to slang

  • ventifact — A stone which has been shaped by the wind or wind driven sand …   Grandiloquent dictionary

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