Depression (geology)

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• A basin may be any large sediment filled depression. In tectonics
  Tectonics
  
  Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures....
  , it may refer specifically to a circular, syncline
  Syncline
  
  In structural geology, a syncline is a downward-curving Fold , with layers that Strike and dip toward the center of the structure. A synclinorium is a large syncline with superimposed smaller folds....
  -like depression: a geologic basin
  Basin (geology)
  
  A structural basin is a large-scale structural formation of rock strata formed by tectonic warping of previously flat lying stratum. Structural basins are geological depressions, and are the inverse of dome s....
  ; while in sedimentology
  Sedimentology
  
  Sedimentology encompasses the study of modern sediments such as sand, mud , and clay, and understanding the processes that deposit them. Sedimentologists apply their understanding of modern processes to interpret geologic history through observations of sedimentary rocks and sedimentary structures....
  , it may refer to an area thickly filled with sediment: sedimentary basin
  Sedimentary basin
  
  The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification....
  .

• A blowout
  Blowout (geology)
  
  Blowouts are sandy depression s in a sand dune ecosystem caused by the removal of sediments by wind.Blowouts occur in partially vegetated dunefields or sandhills....
   is a depression created by wind erosion typically in either a desert
  Désert
  
  ?D?sert? is ?milie Simon's debut single, released in October 2002. The song was a huge success both critically and commercially in her homeland....
   sand
  Sand
  
  Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
   or dry soil (such as a post-glacial loess
  Loess
  
  Loess is a homogeneous, typically nonstratified, porous, friable,slightly coherent, often calcareous, fine-grained, silty, pale yellow or buff, windblown sediment....
   environment).

• A graben
  Graben
  
  A graben is a depression block of land bordered by parallel Fault s. Graben is German language for ditch.A graben is the result of a block of land being downthrown producing a valley with a distinct Escarpment on each side....
   is a down dropped and typically linear depression or basin created by rifting in a region under tensional tectonic forces.

• An impact crater
  Impact crater
  
  In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with larger body....
   is a depression created by an impact such as a meteorite
  Meteorite
  
  A meteorite is a natural object originating in outer space that survives an impact with the Earth's surface. While in space it is called a meteoroid....
   crater.
• A pit crater
  Pit crater
  
  A pit crater is a Depression formed by a sinking of the ground surface lying above a void or empty chamber, rather than by the eruption of a volcano or lava Hawaiian eruption....
   is a depression formed by a sinking, or caving in, of the ground surface lying over a void.
• A kettle
  Kettle (geology)
  
  A kettle is a shallow, sediment-filled body of water formed by retreating glaciers or draining floodwaters....
   is left behind when a piece of ice left behind in glacial
  Glacier
  
  A glacier is a large, slow-moving mass of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity and high pressure....
   deposits melts.

• A depression may be an area of subsidence
  Subsidence
  
  In geology, engineering, and surveying, subsidence is the motion of a surface as it shifts downward relative to a datum such as sea-level. The opposite of subsidence is Tectonic uplift, which results in an increase in elevation....
   caused by the collapse of an underlying structure. Examples include sinkhole
  Sinkhole
  
  A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the surface topography caused by the removal of soil or bedrock, often both, by water....
  s above caves in karst topography
  Karst topography
  
  Karst topography is a landscape shaped by the Solvation of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite....
  , or caldera
  Caldera
  
  A caldera is a cauldron-like volcano feature usually formed by the collapse of land following a volcanic eruption such as the one at Yellowstone National Park....
  s. or maar
  Maar
  
  A maar is a broad, low-relief volcanic crater that is caused by a phreatomagmatic eruption, an explosion caused by groundwater coming into contact with hot lava or magma....
  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
  Sedimentary basin
  
  The term sedimentary basin is used to refer to any geographical feature exhibiting subsidence and consequent infilling by sedimentation. As the sediments are buried, they are subjected to increasing pressure and begin the process of lithification....
  s fill with sediment
  Sediment
  
  Sediment is any particulate matter that can be sediment transport by fluid dynamics, and which eventually is deposited.Sediments are most often transported by water transported by wind and glaciers....
   from an adjacent island arc, or from continental volcanism and uplift.

• A valley
  Valley
  
  In geology, a valley is a Depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge....
   is a type of depression usually carved by erosion.

• An oceanic trench
  Oceanic trench
  
  The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor....
   is a deep depression with steep sides located in the ocean floor. Oceanic trenches are caused by the subduction
  Subduction
  
  In geology, subduction is the process that takes place at convergent boundary by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge....
   (when one tectonic plate is pushed underneath another) of oceanic crust
  Oceanic crust
  
  Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or Sima ....
   beneath either other oceanic crust or continental crust
  Continental crust
  
  The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as Continental shelf....
  .

• 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 rebounds
  Post-glacial rebound
  
  Post-glacial rebound is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostatic depression....
  . 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. Further from the ice, a forebulge may form, which is curved slightly upward.

• A depression may be a pothole
  Pothole
  
  A pothole is a type of disruption in the surface of a roadway where a portion of the road material has broken away, leaving a hole. Most potholes are formed due to fatigue of the pavement surface....
   - either a simple roadway depression or a fluvial
  Fluvial
  
  Fluvial is used in geography and earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them....
   erosional depression in a river
  River
  
  A river is a natural stream of water, usually freshwater, flowing toward an ocean, a lake, or another stream. In some cases a river flows into the ground or dries up completely before reaching another body of water....
   streambed, or area affected by coastal water currents.

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