Depression (geology)
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2008-04-13T20:16:31Z
Mattisse
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add pit crater
'''Depression''' in [[geology]] is a [[landform]] sunken or depressed below the surrounding area. Depressions may be formed by various mechanisms, and may be referred to by a variety of technical terms.
*A basin may be any large sediment filled depression. In [[tectonics]], it may refer specifically to a circular, [[syncline]]-like depression: a [[Basin (geology)|geologic basin]]; while in [[sedimentology]], it may refer to an area thickly filled with sediment: [[sedimentary basin]].<ref name="GTb">{{cite web
| url = http://www.geotech.org/survey/geotech/dictiona.html#sectB
| title = Dictionary of Geologic Terms - B
| accessdate = 2006-08-25
| publisher = geotech.org
}}</ref>
* A [[Blowout (geology)|blowout]] is a depression created by [[wind]] [[erosion]] typically in either a [[desert]] [[sand]] or dry soil (such as a post-glacial [[loess]] environment).<ref name="GTb" />
* A [[graben]] is a down dropped and typically linear depression or basin created by [[rifting]] in a region under tensional tectonic forces.
* An [[impact crater]] is a depression created by an impact such as a [[meteorite]] crater.
* A [[pit crater]] is a depression formed by a sinking, or caving in, of the ground surface lying over a void.
* A [[Kettle (geology)|kettle]] is left behind when a piece of ice left behind in [[Glacier|glacial]] deposits melts.<ref name="GTk">{{cite web
| url = http://www.geotech.org/survey/geotech/dictiona.html#sectK
| title = Dictionary of Geologic Terms - K
| accessdate = 2006-08-26
| publisher = geotech.org
}}</ref>
* A depression may be an area of [[subsidence]] caused by the collapse of an underlying structure. Examples include [[sinkhole]]s above caves in [[karst topography]], or [[caldera]]s.<ref name="GTc">{{cite web
| url = http://www.geotech.org/survey/geotech/dictiona.html#sectC
| title = Dictionary of Geologic Terms - C
| accessdate = 2006-08-25
| publisher = geotech.org
}}</ref> or [[maar]]s in volcanic areas.
* A depression may be a region of tectonic downwarping typically associated with a [[subduction zone]] and [[island arc]]. Fore-arc and back-arc [[sedimentary basin]]s fill with [[sediment]] from an adjacent island arc, or from continental [[volcanism]] and uplift.
* A [[valley]] is a type of depression usually carved by erosion.
* An [[oceanic trench]] is a deep depression with steep sides located in the ocean floor. Oceanic trenches are caused by the [[subduction]] (when one tectonic plate is pushed underneath another) of [[oceanic crust]] beneath either other oceanic crust or [[continental crust]].
* A depression may result from the weight of overlying material such as an ice sheet during continental [[glaciation]] which is subsequently removed resulting in a basin which slowly [[Post-glacial rebound|rebounds]]. The area around the ice sheet, though not covered in ice itself, may also be pulled down by the weight of the ice sheet, which is known as peripheral depression.<ref name="MSUperipheraldepression">{{cite web
| url = http://gemini.oscs.montana.edu/~geol445/hyperglac/glossary.htm#peripheral
| title = Glossary of Important Terms in Glacial Geology - Peripheral Depression
| accessdate = 2006-08-25
| year = 1999
| publisher = Montana State University
}} Cites American Geological Institute’s Glossary of Geology (3rd edition, revised in 1987).</ref> Further from the ice, a forebulge may form, which is curved slightly upward.<ref name="MSUforebulge">{{cite web
| url = http://gemini.oscs.montana.edu/~geol445/hyperglac/glossary.htm#forebulge
| title = Glossary of Important Terms in Glacial Geology - Forebulge
| accessdate = 2006-08-25
| year = 1999
| publisher = Montana State University
}} Cites American Geological Institute’s Glossary of Geology (3rd edition, revised in 1987).</ref>
* A depression may be a [[pothole]] - either a simple roadway depression or a [[fluvial]] erosional depression in a [[river]] [[streambed]], or area affected by coastal water currents.
== References ==
* {{cite web
| url = http://www.geotech.org/survey/geotech/dictiona.html
| title = Dictionary of Geologic Terms
| accessdate = 2006-08-25
| publisher = geotech.org
}}
* {{cite web
| url = http://gemini.oscs.montana.edu/~geol445/hyperglac/glossary.htm
| title = Glossary of Important Terms in Glacial Geology
| accessdate = 2006-08-25
| year = 1999
| publisher = Montana State University
}} Cites American Geological Institute’s Glossary of Geology (3rd edition, revised in 1987).
=== Citations ===
<references />
[[Category:Depressions|*]]
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