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In
geology Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek ...

geology
, a depression is a
landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws ...

landform
sunken or depressed below the surrounding area. Depressions form by various mechanisms. Erosion-related: * Blowout: a depression created by
wind erosion Wind is the flow of gases on a large scale. On the surface of the Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's surface is land consisting of continent ...
typically in either a partially vegetated sand
dune A dune is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the ...

dune
ecosystem or dry soils (such as a post-glacial
loess Loess (, ; from German ''Löss'' ) is a clastic, predominantly silt-sized sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by ...
environment). *
Glacial valley 240px, A glaciated valley in the Altai Mountains showing the characteristic U shape. 240px, U-shaped valley in Leh valley, Ladakh, NW Indian Himalaya. The glacier visible at the head of the valley is the last remnant of the formerly much more e ...

Glacial valley
: a depression carved by
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
by a
glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glacier
. *
River valley A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over ...
: a depression carved by
fluvial In geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
by a river. * Area of
subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...
caused by the collapse of an underlying structure such as
sinkhole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as vrtače and shakeholes, and to openings ...

sinkhole
s in
karst Karst is a topography Topography is the study of the forms and features of land surfaces. The topography of an area could refer to the surface forms and features themselves, or a description (especially their depiction in maps). Topography ...

karst
terrain. *
Sink A sink – also known by other names including sinker, washbowl, hand basin, wash basin, and simply basin – is a bowl-shaped plumbing fixture A plumbing fixture is an exchangeable device which can be connected to a plumbing system to deli ...
: an
endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin A drainage basin is any area of land where precipitation In meteorology Meteorology is a branch of the atmospheric sciences Atmospheri ...
depression generally containing a persistent or intermittent (seasonal)
lake A lake is an area filled with water, localized in a basin, surrounded by land Land is the solid surface of Earth that is not permanently submerged in water. Most but not all land is situated at elevations above sea level (variable ove ...

lake
, a salt flat (playa) or
dry lake A dry lake bed, also known as a playa, is a basin or depression that formerly contained a standing surface water body, which disappeared when evaporation processes exceeded recharge. If the floor of a dry lake is covered by deposits of alkaline ...

dry lake
, or an ephemeral lake. *
Panhole A panhole is a shallow depression or basin eroded into flat or gently sloping cohesive rock.Twidale, C.R., and Bourne, J.A., 2018''Rock basins (gnammas) revisited. ''Géomorphologie: relief, processus, environnement, Articles sous presse, Varia, m ...
: a shallow depression or basin eroded into flat or gently sloping cohesive rock.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.
Collapse-related: *
Sinkhole A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as vrtače and shakeholes, and to openings ...

Sinkhole
: a depression formed as a result of the collapse of rocks lying above a hollow. This is common in
karst Karst is a topography Topography is the study of the forms and features of land surfaces. The topography of an area could refer to the surface forms and features themselves, or a description (especially their depiction in maps). Topography ...

karst
regions. *
Kettle A kettle, sometimes called a tea kettle or teakettle, is a type of pot specialized for boiling water, commonly with a ''lid'', ''spout'', and ''handle'', or a small electric kitchen appliance of similar shape that functions in a self-contained ...
: a shallow, sediment-filled body of water formed by melting glacial remnants in
terminal moraine A terminal moraine, also called end moraine, is a type of moraine A moraine is any accumulation of unconsolidated debris (regolith and Rock (geology), rock), sometimes referred to as glacial till, that occurs in both currently and formerly gl ...
s. * Thermokarst hollow: caused by volume loss of the ground as the result of
permafrost Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean The ocean (also the or the world ocean) is the body of that covers approximately 70.8% of the surfa ...

permafrost
thawing. Impact-related: *
Impact crater An impact crater is an approximately circular depression (geology), depression in the surface of a planet, natural satellite, moon, or other solid body in the Solar System or elsewhere, formed by the hypervelocity collision, impact of a smaller ...

Impact crater
: a depression created by an impact such as a
meteorite A meteorite is a solid piece of debris from an object, such as a comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces ...
crater. Sedimentary-related: *
Sedimentary basin Sedimentary basins are regions of the Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remainin ...
: in
sedimentology Sedimentology encompasses the study of modern sediment Sediment is a naturally occurring material that is broken down by processes of weathering Weathering is the deterioration of rocks A rock is any naturally occurring solid mass o ...
, an area thickly filled with
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...

sediment
in which the weight of the sediment further depresses the floor of the basin. Structural or tectonic-related: *
Structural basin A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as o ...
: a
syncline In structural geology Structural geology is the study of the three-dimensional distribution of Rock (geology), rock units with respect to their Deformation (geology), deformational histories. The primary goal of structural geology is to use meas ...

syncline
-like depression; a region of tectonic downwarping as a result of
isostasy Isostasy (Greek ''ísos'' "equal", ''stásis'' "standstill") or isostatic equilibrium is the state of gravitational Gravity (), or gravitation, is a natural phenomenon by which all things with mass Mass is both a property Prope ...

isostasy
(the Hawaiian Trough is an example) or subduction (such as the
Chilean Central Valley The Central Valley ( es, Valle Central), Intermediate Depression, or Longitudinal Valley is the depression between the Chilean Coastal Range and the Andes The Andes, Andes Mountains or Andean Mountains ( es, Cordillera de los Andes) are the List ...
). *
Graben In geology Geology (from the γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is a branch of concerned with both the liquid and , the of which it is composed, and the processes by which they change over ti ...

Graben
or
rift valley A rift valley is a linear shaped lowland between several Highland, highlands or mountain ranges created by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The ...
: fallen and typically linear depressions or basins created by
rifting In geology Geology (from the γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is a branch of concerned with both the liquid and , the of which it is composed, and the processes by which they change over ...
in a region under tensional
tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building A mountain is an elevated portion of the Earth's crust, gen ...
forces. *
Pull-apart basin In geology, a basin is a region where subsidence File:SubsidedRoad.jpg, Mam Tor road destroyed by subsidence and shear stress, shear, near Castleton, Derbyshire, Castleton, Derbyshire Subsidence is the sudden sinking or gradual downward settl ...
caused by offset in a or
transform fault A transform fault or transform boundary, sometimes called a strike-slip boundary, is a fault Fault commonly refers to: *Fault (geology), planar rock fractures showing evidence of relative movement *Fault (law), blameworthiness or responsibility ...

transform fault
(example: the
Dead Sea The Dead Sea ( he, יָם הַמֶּלַח lit. Sea of Salt; ar, البحر الميت , lit. ''the Dead Sea'',The first article ''al-'' is unnecessary and usually not used. or Buhayrat, Bahret or Birket Lut, ''lit.'' "Lake/Sea of Lot") is a s ...

Dead Sea
area). *
Oceanic trench , while the lithosphere is subducted back into the asthenosphere at trenches Oceanic trenches are prominent long, narrow topography, topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding ocean ...
: a deep linear depression on the ocean floor. Oceanic trenches are caused by
subduction Subduction is a geological process in which the oceanic lithosphere A lithosphere ( grc, λίθος [] for "rocky", and [] for "sphere") is the rigid, outermost shell of a terrestrial planet, terrestrial-type planet or natural satellite. O ...

subduction
(when one tectonic plate is pushed underneath another) of
oceanic crust The oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates This is a list of tectonic plates on Earth's surface. Tectonic plates are pieces of Earth's crust 350px, Plates in the crust of Earth Earth's crust i ...
beneath either oceanic crust or
continental crust Continental crust is the layer of igneous Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the ...
. * A basin formed by an
ice sheet In glaciology Lateral moraine on a glacier joining the Gorner Glacier, Zermatt">Gorner_Glacier.html" ;"title="moraine on a glacier joining the Gorner Glacier">moraine on a glacier joining the Gorner Glacier, Zermatt, Swiss Alps. The moraine is ...

ice sheet
: an area depressed by the weight of the ice sheet resulting in
post-glacial rebound Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheet In , an ice sheet, also known as a continental glacier, is a mass of that covers surroundi ...
after the ice melts (the area adjacent to the ice sheet may be pulled down to create a peripheral depression.) Cites American Geological Institute's Glossary of Geology (3rd edition, revised in 1987). Volcanism-related: *
Caldera A caldera is a large cauldron A cauldron (or caldron) is a large cast iron Cast iron is a group of iron-carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy cons ...

Caldera
: a
volcanic A volcano is a rupture in the crust of a planetary-mass object A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet ar ...

volcanic
depression resulting from collapse following a volcanic eruption. *
Pit crater A pit crater (also called a subsidence crater or collapse crater) is a Depression (geology), depression formed by a sinking or collapse of the surface lying above a void or empty chamber, rather than by the eruption of a volcano or lava Hawaiia ...
: a volcanic depression smaller than a caldera formed by a sinking, or caving in, of the ground surface lying over a void. *
Maar A maar is a broad, low-relief Relief is a sculptural technique where the sculpted elements remain attached to a solid background of the same material. The term ''wikt:relief, relief'' is from the Latin verb ''relevo'', to raise. To create a ...
: a depression resulting from
phreatomagmatic eruption Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions con ...
or
diatreme A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe Volcanic pipes or volcanic conduits are subterranean geological Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "d ...
explosion.


See also

* Cryptodepression * List of places on land with elevations below sea level *
Ponor A ponor is a natural opening where surface water enters into underground passages; they may be found in karst Karst is a topography formed from the dissolution of soluble rocks such as limestone Limestone is a common type of carbonate ...


References

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