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Depression (geology)

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Landform sunken or depressed below the surrounding area

Ingeology, adepression is alandform sunken or depressed below the surrounding area. Depressions form by various mechanisms.

Erosion-related:

Blowout: a depression created bywind erosion typically in either a partially vegetatedsand dune ecosystem or dry soils (such as a post-glacialloess environment).^[1]
Glacial valley: a depression carved byerosion by aglacier.
River valley: a depression carved byfluvial erosion by a river.
Area ofsubsidence caused by the collapse of an underlying structure, such assinkholes inkarst terrain.
Sink: an endorheic depression generally containing apersistent or intermittent (seasonal)lake, asalt flat (playa) ordry lake, or anephemeral lake.
Panhole: a shallow depression or basin eroded into flat or gently sloping, cohesive rock.^[2]

Collapse-related:

Sinkhole: a depression formed as a result of the collapse of rocks lying above a hollow. This is common in karst regions.
Kettle: a shallow, sediment-filled body of water formed by melting glacial remnants interminal moraines.^[3]
Thermokarst hollow: caused by volume loss of the ground as the result ofpermafrost thawing.

Impact-related:

Sedimentary-related:

Sedimentary basin: insedimentology, an area thickly filled withsediment^[1] in which the weight of the sediment further depresses the floor of the basin.

Structural or tectonic-related:

Structural basin: asyncline-like depression; a region of tectonic downwarping as a result ofisostasy (theHawaiian Trough is an example) or subduction (such as theChilean Central Valley).
Graben orrift valley: fallen and typically linear depressions or basins created byrifting in a region under tensionaltectonic forces.
Pull-apart basin caused by offset in astrike-slip ortransform fault (example: theDead Sea area).
Oceanic trench: a deep linear depression on the ocean floor. Oceanic trenches are caused bysubduction (when one tectonic plate is pushed underneath another) ofoceanic crust beneath either the oceanic crust orcontinental crust.
A basin formed by anice sheet: an area depressed by the weight of the ice sheet resulting inpost-glacial rebound after the ice melts (the area adjacent to the ice sheet may be pulled down to create a peripheral depression.)^[4]

Volcanism-related:

Caldera: avolcanic depression resulting from collapse following avolcanic eruption.^[5]
Pit crater: a volcanic depression smaller than a caldera formed by a sinking, or caving in, of the ground surface lying over a void.
Maar: a depression resulting fromphreatomagmatic eruption ordiatreme explosion.

^^a ^b"Dictionary of Geologic Terms – B". US Geochemical. Retrieved2017-09-09.
^Twidale, C.R., and Bourne, J.A., 2018.Rock basins (gnammas) revisited.Géomorphologie: Relief, Processus, Environnement, Vol. 24, No. 2. January 2018. Retrieved 9 June 2020.doi:10.4000/geomorphologie.11880
^"Dictionary of Geologic Terms – K". US Geochemical. Retrieved2017-09-09.
^"Glossary of Important Terms in Glacial Geology – Peripheral Depression". Montana State University. 1999. Archived fromthe original on 2006-08-29. Retrieved2006-08-25. Cites American Geological Institute's Glossary of Geology (3rd edition, revised in 1987).
^"Dictionary of Geologic Terms – C". US Geochemical. Retrieved2017-09-09.

v t e Earth'slandforms
List of landforms
Mountainous	Butte Flat Hill Mountain range Plateau Ridge Tableland Valley
Continental plain	Ice sheet Plain Steppe Tundra
Fluvial	Alluvial fan Beach Canyon Cave Channel Cliff Floodplain Lake island Levee Meander Oasis Pond Rapids River delta mouth Strait Swamp Valley Waterfall
Glacial	Arête Cirque Esker Fjord Glacier Ice field Tunnel valley
Oceanic and coastal landforms	Atoll Bay Cape Channel Coast Continental shelf Coral reef Estuary Island Isthmus Lagoon Mid-ocean ridge Oceanic trench Peninsula Seamount Volcanic island
Volcanic	Caldera Geyser Guyot Lava dome Lava field Submarine volcano Volcanic crater Volcanic crater lake Volcanic dam Volcanic island Volcanic plateau Volcanic plug Volcano Wall rock
Aeolian	Desert Dry lake Dune Sandhill Tundra
Artificial	Artificial island Artificial reef Bridge Building Canal Dam Ditch Land reclamation Levee Polder Quarry Reservoir Road Tunnel
See also:Geographical feature

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