Solothurnersee

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The Solothurnersee is the subject of a scientific model to explain the sedimentological conditions in the area of ​​the southern foot of the Jura . The former existence of such a prehistoric lake over 100 kilometers long in the Swiss plateau has been the subject of controversial discussion in the history of research.

genesis

The lake could have been formed when the Rhone Glacier retreated after the last Ice Age around 15,000 BC due to the warming of the climate. The meltwater from the Rhone and Aare glaciers would have been dammed above the end moraine at Wangen an der Aare east of Solothurn and would have formed a lake that stretched at the southern foot of the Jura to La Sarraz in the canton of Vaud and had a water level at around 450  m above sea level. M. reached.

In individual places, after the ice had shrunk, rock material broke off from the Jura mountain flanks. One example of this is the Wandflue near Bettlach near Grenchen . This steep rock face was created after a rock fall. The Wandflue is therefore much more recent than the Belchenflue , which was formed by erosion during the Jura folding .

Landscape history

Around 10,000 years before Christ, when the glaciers had disappeared down to the remains in the Alpine valleys and only debris from the foothills of the Alps reached the Central Plateau, the mighty meltwater flow would have deepened the moraine dam at Wangen an der Aare and the contents of the lake would have been it flowed down the valley as a very large, long-lasting flood .

Already during the glaciation and especially when the glacier retreated, the rivers carried a lot of debris from the Alps and the Jura into the glacial trough valleys of the Central Plateau, which they filled in large parts with alluvial cones and other deposits according to the laws of sedimentation . In the end, Lake Biel , Lake Neuchâtel and Lake Murten were the last remaining bodies of water and vast floodplain landscapes such as the Grosse Moos , the Orbe plain and the Grenchner Witi . The formation of Lake Biel was facilitated by the chain of molasse hills from Lengnau to Ins .

At construction sites in Biel , for example , the deposits from older lake basins can still be felt today. The water table is just below the surface. From a certain depth, excavation pits must therefore be protected against the ingress of water using diaphragm walls .

See also

literature

  • Barbara Wohlfarth, Antke Schwalb, Anne Marie Schneider: The history of lakes and rivers in the West Swiss Zealand between 5000 and 12000 years ago . In: Communications from the Natural Research Society in Bern. New Series, Vol. 50, 1993, pp. 45-59.
  • Fritz Antenen: Geology of the Seeland , Biel 1936.
  • Werner Lüdi : The Grosse Moos in Seelande in western Switzerland and the history of its creation , in: Publications of the Geobotanical Institute Rübel in Zurich, Vol. 11, 1935.
  • Hans Schardt : Sur l'origine des lacs du pied du Jura , in: Bulletin de la Société neuchâteloise des Sciences naturelles, Vol. 26, 1898.
  • Fritz Nussbaum: About the gravel in the Seeland , in: Mitteilungen der Naturforschenden Gesellschaft in Bern, 1907.

Web links

Individual evidence

  1. ↑ Barbara Wohlfarth-Meyer: The Solothurnersee - a geological myth. In: J. Schibler, J. Sedlmaier, H. Spycher: Festschrift for Hans R. Stampfli, 1990, pp. 319-325.
  2. ↑ B. Ammann, W. Haeberli, B. Wohlfarth, R. Merki, J. Presler, U. Schälchli, A. Kühne: Landscape development in the Seeland since the last Ice Age - models and reality . In: Models of Geomorphology - Examples from Switzerland, Freiburg 1991, pp. 73-100.
  3. ^ Environment, Biology and Geology: Last Ice Age Maximum. In: map.geo.admin.ch. swisstopo , accessed on December 9, 2011 .