A dreikanter is a type of
ventifact
A ventifact (also wind-faceted stone, windkanter) is a rock (geology), rock that has been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals. The word "Ventifact" is derived from the Latin word "Ventus" meaning 'wind ...
that typically forms in
desert
A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...
or
periglacial
Periglaciation (adjective: "periglacial", referring to places at the edges of glacial areas) describes geomorphic processes that result from seasonal thawing and freezing, very often in areas of permafrost. The meltwater may refreeze in ice wedg ...
environments due to the abrasive action of
blowing sand.
Dreikanters exhibit a characteristic
pyramid
A pyramid () is a structure whose visible surfaces are triangular in broad outline and converge toward the top, making the appearance roughly a pyramid in the geometric sense. The base of a pyramid can be of any polygon shape, such as trian ...
al shape with three wind-abraded facets. The word ''Dreikanter'' is
German
German(s) may refer to:
* Germany, the country of the Germans and German things
**Germania (Roman era)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizenship in Germany, see also Ge ...
for "three-edged."
Similarly, a zweikanter ("two-edged") has two wind facets, an einkanter ("one-edged"), has only one wind facet.
[Greeley, R., N. T. Bridges, R. O. Kuzmin, and J. E. Laity, Terrestrial analogs to wind-related features at the Viking and Pathfinder landing sites on Mars, J. Geophys. Res., 107(E1), doi:10.1029/2000JE001481, 2002.]
Most places on Earth have several weathering processes acting at the same time, so finding good examples of dreikanters is often difficult.
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
is a good location for finding such ventifacts since wind is usually the only active weathering agent. Many specimens in the Northeastern United States were formed during the Pleistocene era when the absence of vegetation made for little cover from wind-blown sediment.
Dreikanters have also been observed on Mars in rover footage from the planet.
Common features
Some common features of dreikanters include
fluting, high polish, sharp ridges, pits, grooves, and helical forms.
image:Bradley_1930_dreikanter.jpg, 300px, Unusually large dreikanter of granite, Sweetwater County, Wyoming. This dreikanter measures 71 cm by 46 cm deep and 37 cm wide. Photo by Bradley, W.H., USGS (1930).
[U.S. Geological Survey Photographic Library ( http://libraryphoto.cr.usgs.gov/ )]
Formation
In areas where there is a prevailing wind, sand and debris cause a rock face to become flattened and polished. This changes the mass distribution of the rock, and may cause it to turn another surface toward the wind. If this process continues undisturbed, the resulting rock will have three distinct flattened and polished faces.
Dreikanters generally form in dry, arid environments from hard rocks.
See also
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References
External links
An image of a dreikanterGlossary of Meteorology
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Geomorphology
Petrology
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