Depression (geology)
From Freepedia
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 blowout is a depression created by wind erosion typically in either a desert sand or post-glacial loess environment.
- 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 depression may be an area of subsidence caused by the collapse of an underlying structure. Examples include sinkholes in karst topography, calderas or maars in volcanic areas, or kettles in glaciated terraines.
- A depression may be a region of tectonic downwarping typically associated with subduction zones and fore-arc and back-arc basins associated with island arcs. These typically result in sedimentary basins as they fill with sediment from adjacent island arc or continental volcanism and uplift.
- 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.
- 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.
One of many impressive depressions is the Great Rift Valley of East Africa. Perhaps even more impressive is the Atlantic Ocean basin.
