Sinkhole

As a sinkhole (from Slavic dolina 'valley', ' Sinkhöhle " ) or sinkholes is called a chimney-, cone-or bowl -shaped depression of mostly circular or elliptical ground plan in karst areas. Their diameter usually varies between 2 and 200 meters, can at trough-like Subrosionssenken but amount to several kilometers. Its depth ranges from 2 to more than 300 meters. The largest by volume are Sarisariñama - tepui in Venezuela and Sótano del Barro in Mexico. The deepest water-filled sinkhole is the Zacaton in Mexico.

Formation of sinkholes

Sinkholes occur always by solution processes at the Earth's surface, in contrast to the sinkhole, a triggered by events in the Earth's interior solution appearance. This difference is often not recognized, so that the concept formation was Erdfalldoline.

Sinkholes do not form a part, preferably in subtropical climates, but in dry desert and desert steppe areas. But in the small form they are found in the more temperate latitudes (eg Paderborn Plateau ). Their formation requires an adequate wetting of the rock surfaces by rain, melt water or dew, but can also be caused by contact of groundwater with highly water-soluble rock. As such, in particular limestone, marble, dolomite, or rock salt mentioned.

This karst form arises in areas with strong, acting in the subsurface solutions. The purer and fissured (column- rich ), for example, the lime, the faster takes the Verkarstungsprozess in the carbonated water initiates the lime solution ( corrosion). Is the rock underground sufficiently solved, crevices, chimneys and cavities of different sizes form.

Sometimes sinkholes are also widely ramified cave systems in conjunction. Sinkholes often occur on steep slopes or in high mountains, as the surface flow of water to quickly happening here is usually to set the chemical solution processes in motion. An exception is, for example, the sinkhole of Funtensees.

Sinkhole and Dolinentypen

Korrosionsdolinen

• By solution and rinsing of the surface rock is Trichterdolinen or significantly flatter Schüsseldolinen can form (or Uvalas ).
• Karst chimneys lead as tubular, widening or narrowing natural bays vertically or obliquely into the ground and often result in caves whose light wells form. Ends of the vents blind, they are called sinkholes.

Erosionsdolinen

• Ponordolinen have a similar shape to Korrosionsdolinen but differ significantly by their genesis. By the by fissures and columns ( shrinkage holes) flowing water rinses the existing Locker masses, the typical hollow forms come here mainly by erosion. Since there partially accumulates clay, the cavities are sealed and may incur lakes.

Sinkholes

• If the ceilings of caves unstable about as a result of tectonic movements caused by burglary sinkholes that are expected for the reasons described above, not to the sinkholes.

• Grikes, soil and land subsidence are formed by the collapse of underground cavities that are extend for hundreds of meters below the surface and have been previously developed by the dissolution of water- rock or by flushing of loose materials. The ceilings of the cavities eventually give the pressure of the overlying strata according to (example).

Mardellen

On limestone plateaus are found sometimes called Mardellen mostly artificial hollows, the anthropogenically caused by removal of material from the Iron Age and then served as Flachsröste, livestock watering or water reservoir.

Dolinenvorkommen

Sinkholes than typical karst formations occur everywhere where mighty enough limestone or gypsum rocks form underground. They found, for example in southern Croatia and Istria and Bosnia and Herzegovina, the classical countries of the Karst and Karst Research. One of the most impressive sinkholes is here about two million years collapse in near Imotski Red sinkhole, the Red Sea, which is 280 meters deep. In its vicinity is the Blue sinkhole, which is up to 100 meters deep with strongly fluctuating water levels. Sinkholes exist in all other Mediterranean countries such as Greece, France (eg Chasm of Padirac ), Spain. In the Romanian Western Carpathians, a National Park of the Karst exists with a 200 meter deep complex of three sinkholes ( Cetatile Ponorului ). Here two underground and aboveground water run together.

Numerous sinkholes formed in Central Europe, in Austria or Germany, such as in the Dead Mountains, in the central Swabian Alb, the green hole in Lunz am See, Lower Austria, in the Kraichgau ( both burglary and Lösungsdolinen: Dolinenfelder Eisinger hole Neulinger mountain etc.), in Hemer ( Felsenmeer ), in the southern Harz mountains, the "Wolf pit" at Flintsbach upper Bavaria, in the Czech Republic ( chasm ) and in the Swiss Jura.

Extensive Dolinenvorkommen are also known from other continents and countries, such as Mexico, the U.S. or China.

Special

Due to the sometimes considerable depth of the air exchange is sometimes significantly restricted, which can lead to the formation of specific microclimates. Example, there is in the Swabian sinkhole Weidenwang (municipality Sonnenbühl ) to more than 220 days a year frost, because the cold air can not escape. In the sinkhole green hole at Lunz in Lower Austria the lowest documented temperature in Central Europe in 1932 was minus 52.6 degrees Celsius measured.

Examples

Red Sea ( Crveno Jezero ) in the south of Croatia, about 280 m deep

Sacred Cenote in Chichen Itza, Mexico

Two sinkholes near the village of Didyma, 25 km from Ermióni ( Peloponnese, Greece)

Pulo di Altamura: diameter 550 m, 92 m deep.