Isar Loisach Glacier
The Isar-Loisach Glacier was a foreland glacier in the Bavarian Alpine foothills during the Pleistocene . It originated in the vicinity of the main Alpine ridge and pushed over the fully glaciated Inn Valley and through the Bavarian foothills into the Alpine foothills.
The Isar-Loisach Glacier has been documented in the last three glacial periods, the Mindel glacial period , the Riss glacial period and the most recent, the Würm glacial period .
distribution
The Isar-Loisach Glacier was supplied by the large Inn Glacier in the Central Alps. With influence he came out of the alpine gates of today's valleys of the Isar , the Kochelsee basin and the Loisach from the mountains. The glacier tongues united, covered the landscape of the immediate foreland and dug the basins of the Ammersee , the Starnberger See , the no longer existing Wolfratshausen lake and the Isar valley. The meltwater from the glacier transported the gravel that forms the Munich gravel plain beyond the icy area . Its outflows formed the glacial valley of the Danube with the other northern foreland glaciers of the Alps .
Würm cold time
The traces of glaciation in the Würm Ice Age are best preserved. During the Würm Ice Age, the Isar-Loisach Glacier penetrated the furthest north of the large foreland glaciers in what is now Germany, the Inn , Isar-Loisach, Iller-Lech and Rhine glaciers . The foreland glaciation then reached a thickness of just over 1000 m above today's level.
At its maximum extent around 20,000 years ago, the glacier reached to today's Landsberg am Lech , Grafrath , Leutstetten , Hohenschäftlarn and shortly before Sachsenkam . Only the Hohe Peißenberg and the now no longer prominent Tischberg , a knoll from the Upper Freshwater Molasse, to the southeast of Lake Starnberg , protruded from the ice cover as so-called nunataks .
As it retreated, the Isar-Loisach Glacier left behind the landscape of today's Alpine foothills, shaped by the moraines . Formative elements are ground , end and side moraines , drumlins and glacier terraces .
Of particular importance are the ice crumbling landscape with huge blocks of dead ice from which the Osterseen emerged, the Eberfinger drumlin field with around 360 drumlins with a size of over 100 to 1900 m and the enormous amounts of mud with high clay proportions that remained when the glacier melted, and the soils on which the large moor landscapes of the Alpine foothills with Murnauer Moos , Ampermoos , the Loisach-Kochelsee moors and the small-scale low and high moors or rain moors , interlocked with other landscape forms, emerged. The meltwater that ran off created the Teufelsgraben and the Gleißental , the Mühltal and other small and larger drains that drain mostly over the Isar and partly over the Mangfall and Inn to the Danube.
Mindel and Riss cold times
Since the largest extent of the Mindel and Riss ice ages was less than that of the subsequent Würm Ice Age, their deposits were largely overformed by the later glaciation and are difficult to detect. The large-format areas of the Munich gravel plain also originate from these cold times, as do the gravel river terraces of the Isar, Würm and Ampertal valleys . Under the pressure of subsequent layers and with the help of fine limestone deposits, the deeper layers of this gravel in the areas close to the Alps mostly stick to the secondary rock Nagelfluh , which is characteristic of the Isar valley and parts of the immediate Alpine foothills.
History of science
The traces of the Isar-Loisach glacier were important for the research of glacial morphology in the 19th century, especially the Glacial Series . The emergence of terminal moraines was recognized by the breakthrough of the Würm into the Mühlthal at the northern end of the Leutstettener Moos , which Albrecht Penck researched by Drumlins using the Eberfinger Drumlinfeld and the sequence of related glacial morphological phenomena using the Alpine foothills and coined the term glacial series in 1882.
Individual evidence
- ↑ Hermann Jerz : The Ice Age in Bavaria , Volume 2 of the Geology of Bavaria , Schweizerbart'sche Verlagsbuchhandlung, 1993. ISBN 3-510-65157-X . Chapter Glacial, fluvioglacial and galzifluviatile areas (Alpine foothills and Alps)
- ^ Rolf KF Meyer & Hermann Schmidt-Kaler. Wanderings in the history of the earth. On the trail of the Ice Age south of Munich - eastern part. Pfeil Munich 1997. p. 31
- ↑ Ludger Feldmann: The geological development of the landscape around Eberfing . In: Luise Hohenleitner: Eberfinger Heimatbuch , published by the municipality of Eberfing, 1998. Pages 255–263
- ↑ Rolf KF Meyer, Hermann Schmidt-Kaler: Walks into the history of the earth - Volume 8: On the trail of the Ice Age south of Munich, eastern part . Pfeil Verlag, 1997. ISBN 3-931516-09-1 , pages 15-26