Rhine Glacier

Foothills of the Rheingletscher during the Riss glaciation with the original Danube river system blocked off

The Rheingletscher , also known as the Rhein-Linth-Glacier , was a glacier in the Appenzell Alps that had a strong influence on the topography of the eastern Swiss plateau and from Upper Swabia (Germany) to far north of Lake Constance . Lake Constance and Lake Zurich are glacial lakes of the Rhine and Linth glaciers .

expansion

The time and place of origin of the Rhine Glacier is around 29,000 years ago in the Chur area. About 24,000 years ago, the maximum level was reached with a range of Schaffhausen . The glacier had the greatest extent with an ice surface of about 16,400 km² and about 11% of the alpine ice cap during the Riss ice age . During this cold period, the glacier covered a catchment area from the Arlberg to the Gotthard , enclosed the inner-Alpine valleys between the Rheinwaldhorn and Chur, the Alpine Rhine valley that stretched from Lake Constance to Chur and the foreland basin around Lake Constance. The glacier penetrated as far as the pre-ice age Danube (line west of Schaffhausen / Stein am Rhein - south of Tuttlingen - north of Sigmaringen - Biberach - east of Leutkirch ). He blocked the river bed of the original Danube . This created large ice reservoirs. The ice surface was at the Würm maximum near Chur at around 2,000 m. The ice height above Lake Constance was still 900 m ( Constance ) to 1,100 m ( Bregenz ). The greatest annual total flow of ice mass was estimated for above Sargans at approx. 7.3 km ³ , the laminar flow velocity there was calculated at 45 to 100 m per year. The current cities of Chur , Glarus , Sargans , St. Gallen , Vaduz , Feldkirch (both Rhine glacier), Zurich (Linth glacier), Schruns (Ill glacier), Winterthur , Ravensburg and the cities on Lake Constance (both Lake Constance ) lay under the ice masses of the glacier -Forland glacier).

The Linth glacier in the Lake Zurich basin

The system is also known as the Rhine-Linth system because an arm of the Rhine Glacier was connected to the current Linth catchment area in a diffluence via the Sargans valley bifurcation . The Linth glacier filled the northwest-facing basins of the Glatt and Limmat valleys . In addition to the Graubünden Rhine region, the eastern part of the system was also supplied with ice from the Vorarlberg valleys of the Ill and the Bregenz Ach .

The last major expansion of the glacier was in the Würm glacial period . The Rhine Glacier extended over all of today's eastern Switzerland and Lake Constance. The main current direction increasingly shifted to the west in the direction of the High Rhine. At Schaffhausen the maximum level was only slightly lower than during the Riss Cold Age. In the Lake Constance area there was great deepening due to the ice thickness of up to 1,200 m and as a result of subglacial melt water flowing off the bottom of the glacier under high pressure. Mountains that protruded over the ice were flown around. The Schesaplana (2,965 m above sea level. NHN), the Säntis (2501 m above sea level. NHN), the Hochgrat im Allgäu (1834 m above sea level. NHN) and the macaroni in the canton of Zurich (1133 m above sea level. NHN) at that time were Nunatakker .

The question of a connection between the Feldberg Glacier and the Alpine glaciation flowing westwards along the High Rhine during the Riss Ice Age has not yet been finally clarified according to current research. For the Würm high glacial, the Olten - Aarau - Baden - Basel region is indicated as always ice-free.

Würm melting stages

After the highest level of the Würm glaciation around 20,000 years ago with a snow line of 1,000 m, the Rhine Glacier retreated in a total of eight proven stages, including the Schaffhausen Stadium (maximum level), Singen Stadium and Konstanz Stadium as the most important. The Lake Zurich , the first still with the Walen was associated, was in constant phase with a Endrandlage in Hurden . These stages were completed 15,000 years ago. Other stands may have been in the area of Lake Constance. At the end of the melting stages, the Rhine Falls came into being .

Today's witnesses to the glacier

Rohrsee near Bad Wurzach

Drumlin Biblis Protected Landscape Area . Relic of the Rhine glacier near Überlingen

Hönggerberg (Zurich) - boulder field of the Linth glacier

In addition to Lake Constance (Rheingletscher), Lake Zurich (Linth Glacier) and the Upper Swabian wealth of lakes, ponds, wetlands and moors ( Federsee , Rohrsee , Wurzacher Ried ), there is numerous other evidence for the existence of the Rhine Glacier. A well-known ground moraine from the Riss glaciation can be found near the large Scholterhaus gravel pit near Biberach , discovered and described by Albrecht Penck . A crack terminal moraine appears on the Swabian Alb west of Riedlingen . During the so-called Zurich stage of the Linth Glacier (around 20,000 years ago) the moraine wall that closes Lake Zurich in the north was created. Marginal moraine walls of the Linth Glacier exist near Schindellegi as far as the urban area of Zurich.

The western foothills of the Rheingletscher gave shape to the Hegau cone with their steep overprints on the east side facing the ice flow. At Rorschach there are ice-edge terraces, flat areas across the slope as glacier relics and also moraine walls made of up to 100 meters high loose material that the Rhine glacier has piled up on the sides.

Many drumlins can be found in the Zurich Oberland and Allgäu, an erratic block swarm with rocks from the Glarus Alps in the Jörentobel on the Greifensee . Examples of erratic boulders on the Rhine Glacier are the boulder in the Koblenwald near Rorschacherberg , the gray stone from Aach (Hegau) of the Worm Ice Age Rheingletscher, which was transported from a distance of about 150 kilometers to the current location and weighs about 30 tons. There are also two boulders in Frauenfeld , and more near Wangen im Allgäu ( BAB 96 ).

literature

Penck , A. & Brückner, E. (1909). The Alps in the Ice Age, 3 volumes, Tauchnitz, Leipzig (first description of the Rhine Glacier).

Christof Benz-Meier: The maximum level of the Rhine Glacier during the Wurm Ice Age: digital reconstruction, modeling and analysis with a geographic information system. University of Zurich-Irchel, Institute of Geography, Zurich 2003, ISBN 3-85543-239-2 .

Oskar Keller: Considerations on the correlation of Middle Pleistocene relics of the Rhine Glacier with the northern Swiss stratigraphy. In: Quaternary Science Journal. Volume 63, No. 1, 2014, pp. 19-43, doi: 10.3285 / eg . 63.1.02 .

Web links

National map of Switzerland: Last Ice Age maximum on map.geo.admin.ch
Wurm Ice Age Rhein-Linth Glacier Stadiale Eisrandkomplexe (image file)

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ The Rhein-Linth-Glacier in the last Hochglacial quarterly publication of the Natural Research Society in Zurich (2005) 150 / 1–2: 19–32

↑ ^a ^b ^c René Hanke: The difference of the Worm Ice Age Rhine glacier near Sargans (Canton St. Gallen) and the late glacial glacier stands in the Walensee valley and in the Rhine valley ( Memento of the original from July 14, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and not yet tested. Please check the original and archive link according to the instructions and then remove this notice. . Ice Age and Present. Volume 1 9 pages 219–226 Öhringen / Württ., October 31, 1968 @1@ 2

↑ ^a ^b ^c ^d ^e Joachim Eberle, Bernhard Eitel, Wolf Dieter Blümel, Peter Wittmann: Germany's South from the Middle Ages to the present. 2nd edition, Spektrum Akademischer Verlag, Heidelberg 2010, ISBN 978-3-8274-2594-2 .