Sink (geosciences)

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From a geographical point of view, every hollow shape in the ground relief is referred to as a depression, as is this deep hollow in the Bärenwinkel on the Karst hiking trail

In the geosciences, a sink is generally a hollow form in the ground relief; a flat piece of the earth's surface, which is surrounded by bumps. In geology in particular, a depression is a part of the earth's surface that has tectonically sunk in relation to its surroundings. Depending on their shape, size or location, tectonic depressions are categorized as basins (rounded, smaller), basins (rounded, larger), ditches (elongated, narrow) or depression ( depression below sea level). Tectonic subsidence is a common cause of the large continental and marine bumps.

The tectonics of the earth's crust cause depressions, among other things. The subsidence fields are surrounded by breaks or bends in the layer.

Definitions

In the geosciences, a sink can be understood to mean different morphological facts, depending on the geographical or geological perspective.

In terms of geography, a depression is a size-independent hollow form in the ground relief, i.e. a negative landform, but without making a statement about its genesis. Levels and flat floors that are surrounded by elevations, no matter how flat, are called depressions. Depressions do not form a type of terrain, but the term only relates a flat surface area to the surrounding area.

In terms of structural geology, a depression is a deepening of the terrain caused exclusively by tectonics, i.e. a part of the earth's surface that has sunk in relation to its surroundings due to shifts in the earth's crust . The subsidence fields are bordered by break lines or seamless bends (also called flexure ), which can also be polygonal .

In addition to uplift , displacement , volcanic deposits and coral reef formation , tectonic subsidence is one of the first-order shaping factors that create the basis for the large unevenness of the ground. Sinks come in different shapes and sizes in all regions of the world.

A differentiated designation of the sinks is based on their morphological structure. Are they more or less circular, they are used as boiler fraction designated or present unbroken bending as Verbiegungssenke, has the hollow character. If the shape is long and narrow, with more or less parallel edges, they are called ditch , ditch fracture , or ditch sinking. The largest depressions, hundreds of square kilometers in size, are known as subsidence basins .

In the case of continental sinks, a distinction is made between endorheic , which are closed on all sides and have no drainage, and exorheic , which are open on one or more sides and whose water can drain into the oceans. The endorheic sinks are found in areas with an arid climate , where they cannot be filled with water and caused to overflow due to insufficient precipitation and / or excessive evaporation and thus only drain inwards. They often contain salt steppes and a salt lake or salt marsh at their bottom.

Continental depressions, the deepest point of which is below sea level, are known as depression . Depending on their distance from the sea, a distinction is made between coastal and inland depressions. A coastal depression is a diked, land-based area in the coastal area. The inland depressions are naturally in very dry areas, which lack the necessary rainfall to fill the basin with water. They are therefore usually taken from deserts or steppes, mostly salt steppes, in their deepest part often from salt lakes or salt marshes. If the water level is below sea level during a depression, it is one of the open sinks. However, if it is located in areas with sufficient rainfall and the water level rises above sea level, it is referred to as a cryptodepression (κρυπτός kryptos "hidden"), i.e. a depression which, on the surface, is hidden.

Deviating from the general appearance, not every sunken clod also shows up morphologically as a sink. The surface appearance can contradict the tectonic structure. If the submerged rocks are more resistant to erosion than the surrounding rocks, a reversal of relief occurs due to erosion and the subsidence field finally dominates its surroundings.

Geological-tectonic depressions
category example Floor
m above sea level M. 		Water level
m above sea level M.
Boiler rupture HalaHu 252312838 fd14e10f7a o.jpg Hala Lake Basin
in Qinghai Province, China .
Water-filled, endorheic depression, deeply embedded in the Qilian Shan Mountains in the Tibetan Plateau . The water level of the end lake would have to rise by almost 200 m (to 4267 m above sea level) to reach the lowest overflow point.		 4013 4078
Bending depression Neckar basin.jpg Neckar basin
between Stuttgart and Heilbronn.
Exorheic depression with drainage over the Neckar , surrounded by large-scale curvatures.		 170
Subsidence basin PannonianPlain1.jpg Carpathian Basin (Pannonian Basin)
in south-eastern Central Europe (Hungary and six other countries).
With an extension of 250,000 km 2, Europe's largest continental depression, exorheic, with drainage over the Danube . Bordered by the Carpathian Mountains , the Dinarides and the Alps . Developed with the participation of large boiler fractures.		 65

Rift Valley Rift Valley		 Main unit groups western layer level country.png Oberrheingraben (Upper Rhine Plain)
between Basel and Frankfurt am Main.
Due to its elongated shape with 300 km in north-south direction and with roughly parallel edges at a distance of 30 to 40 km, the depression is called Graben.		 80
Zeller Horn-6131.jpg Hohenzollern ditch
in Baden-Wuerttemberg
A rift valley (30 km long, 1.5 km wide) with reversed relief. The tectonic depression does not appear as a morphological depression, but as a mountain range.		 - - - - - -
depression Aydingkol1.jpg Turpan Basin
in Xinjiang Province, China .
An inland depression, endorheic depression, with an area of ​​40,000 km 2 below sea level, in the center of the Eurasian continent. Due to the climate, there is no lake on its bottom, but a salt marsh.		 - 154 - - -
Crypto depression Map baikal2.png Lake Baikal Basin
in southern Siberia , Russia.
Exorheic rift valley with Lake Baikal, the largest, deepest and oldest freshwater reservoir on earth. The water level is above sea level and the bottom of the depression is hidden deep below sea level.		 - 1186 + 455

Emergence

See also

Web links

Individual evidence

  1. ↑ a b c d e f g Hermann Wagner : Textbook of Geography. Second part physical geography. Hahnsche Buchhandlung, 1921. (books.google.de)
  2. ↑ a b c d e f g h i j k l m Georg Schulz: Lexicon for determining the shape of the terrain in maps . (= Berlin Geographical Writings. Volume 28). Institute for Geography of the Technical University of Berlin, Berlin 1989, ISBN 3-7983-1283-4 . (books.google.de)
  3. ↑ a b c d Stephanie Grim: Drainless sink instruments in landscape analysis and indicators of recent crust movements . Dissertation University Library Mainz, 2012. (pdf; 17.5MB)
  4. ↑ a b c R. Lehmann: The main processes of the design of the earth's surface. In: The design of the earth's surface. Vieweg + Teubner Verlag, 1925. doi: 10.1007 / 978-3-663-20242-4 . (books.google.de)
  5. ^ A b Hans Murawski, Wilhelm Meyer (Ed.): Geological dictionary. 12th edition. Springer 2017, ISBN 978-3-662-54049-7 , doi: 10.1007 / 978-3-662-54050-3 (books.google.de)
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  8. ↑ Klaus-Peter Konerding, Andrea Lehr (Ed.): Linguistic theory and lexicographical practice: Symposium lectures , Heidelberg 1996. Max Niemeyer Verlag, 1997. doi: 10.1075 / babel.44.4.17cla (books.google.de)
  9. ↑ a b c d Alexander Supan. Basics of physical geography . Veit & Comp., 1884. (books.google.de)
  10. ↑ a b Willi Ule: Ground plan of general geography. 2nd Edition. S. Hirzel, 1915. (pdf)
  11. ↑ Herbert Louis: General Geomorphology: Text part and separate picture part. Vol. 1, Walter de Gruyter, 2013. (books.google.de)
  12. ^ A b Dieter Richter: General Geology. Walter de Gruyter, 2013. (books.google.de)
  13. ↑ a b c Bernd Wünnemann et al: Implications of diverse sedimentation patterns in Hala Lake, Qinghai Province, China for reconstructing Late Quaternary climate. In: Journal of Paleolimnology. Volume 48.4, 2012, pp. 725-749. doi: 10.1007 / s10933-012-9641-2 (pdf)
  14. ^ Wuerttemberg, State Statistical Office: General part and Neckar district. (= The Kingdom of Wuerttemberg: a description by districts, chief offices and communities. Volume 1). 1904. (books.google.de)
  15. ^ Georg Burgmeier, Manfred Schöttle. Geotopes in the Stuttgart administrative district (= soil protection. 12). State Institute for Environmental Protection Baden-Württemberg, 2002. (online)
  16. ↑ a b c Measure estimated with the help of Google Earth 2019.
  17. ↑ G. Uherkovich: Overview of the potamophytoplankton of the Tisza (Theiss) in Hungary. In: Hydrobiologia. Volume 28.2, 1966, pp. 252-280.
  18. ↑ Miklós Kázmér: Birth, life and death of the Pannonian Lake. In: Palaeogeography, palaeoclimatology, palaeoecology. Volume 79.1-2, 1990, pp. 171-188. (pdf)
  19. ^ C. Clauser, H. Villinger: Analysis of conductive and convective heat transfer in a sedimentary basin, demonstrated for the Rheingraben. In: Geophysical Journal International. Volume 100.3, 1990, pp. 393-414. (pdf)
  20. ↑ a b M. B. Allen, BF Windley, Z. Chi, G. Jinghui: Evolution of the Turfan Basin. In: Tectonics. Vol. 12, No. 4, 1993, pp. 889-896. doi: 10.1029 / 93TC00598 (pdf)
  21. ↑ Rebecka Törnqvist et al: Evolution of the hydro-climate system in the Lake Baikal basin. In: Journal of Hydrology. 519, 2014, pp. 1953–1962. (on-line)
  22. ↑ a b P. P. Sherstyankin et al: Computer-based bathymetric map of Lake Baikal. In: Doklady earth sciences. Vol. 408, No. 1, MAIK Nauka / Interperiodica, 2006. doi: 10.1134 / S1028334X06040131 (pdf)