Inn glacier

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The Inn Glacier , also known as the Inntal Glacier , was the Ice Age glacier of the Alpine river Inn . Coming from the Swiss Upper and Lower Engadine (Canton of Graubünden), it flowed through Austria's Tyrol (today's Inn Valley ) and then spread out into the Bavarian Alpine Foreland . The Inn Glacier probably reached its greatest thickness and extent in the Mindel glacial period (around 450,000 to 400,000 years ago) and again in the Riss glacial period (350,000 to 120,000 years ago today). The Inn Glacier area is a type region of the Würm Glacial , as the end of the ice ages can be determined particularly well here.

Main stream (Inntal glacier)

The Upper Engadine Lake District: Silvaplana (front) and Silsersee (back), on the right the foothills of the Champfèrersee

The ice flow had its origins in the glaciations around the Gotthard massif and the Bernese Alps . At the maximum levels it was fully integrated into the local ice stream network. In the back Engadine it will have queued m to about 2700, and large masses of ice were north to the Rhine glacier pushed. The chain of lakes from Sils - Silvaplana - St. Moritz (Upper Engadine Lake Escape) goes back to dead ice masses from the ultimate ice breakup .

In the further course, ice flows, in particular from the Bernina group , appeared. In the area of ​​the Finstermünz Pass , at the exit of the Lower Engadine , a glacier surface of 2500–2600 m is assumed.

In the Upper Inn Valley , mighty rivers from Paznauntal , Pitztal and Ötztal were added, around Vent and Gurgl there are the highest grinding marks at 2900 m, whereby ice masses were again displaced over the Klostertal into the Rhine area, as well as to the south to the Etsch Glacier .

Glacier profile with Inntalboden and low mountain ranges around Innsbruck and Hall in Tirol (location at 1500 m, so still in the ice body of the high stands)

In the central Inn Valley, further glaciers from the Sellraintal , Stubaital and Wipptal came in from the south , displacing a tributary towards Seefeld. Around Innsbruck the glacier level was likely to have been at least 2200 m, as can be estimated from the narrowly overflowing Scharten Erlsattel  (approx. 1800 m) and Lafatscher Joch  (2081 m) on the Nordkette . The ice stream network from the central to the northern Alps will also have passed through in this area. This transport was also active in the Last Glacial Maximum  (LGM, Würm High Glacial , 20,000 years ago).

In the direction of the Lower Inn Valley , the height decreased towards 2000 m, with the glacier from the Zillertal again pushing a tributary towards Achensee. These two glacier streams already met at their highest levels around Schwaz : the Loas saddle  (1683 m) was flooded and the Kellerjoch  (2344 m) stood as an island mountain ( Nunatak ) in the glacier. A huge ice field was likely to have existed as far as below the mouth of the Ziller (up to 1900 m). After that, the thickness decreased comparatively quickly as far as Kufstein .

Geological profile in the Melach Gorge ( southwest low mountain range ) between Oberperfuss and Grinzens , towards northwest: basement interglacial terrace sediments hanging moraine from the last glaciation late glacial sediments
White stripes.svg



              Level of Melachaccording to Hans Bobek / Federal Geological Institute  (1935)

Characteristic traces of the glacier are the terraced landscapes from the sun terrace in the Upper Court to Kufstein, which are 100–500 meters above the Inntalgrund in the Central Inn Valley , the actual Tyrolean low mountain range . They are partly massive basement rock, partly sedimentary bodies, and in the Mindel-Riss interglacial (approx. 330,000 years ago) they were again covered with mighty gravel, only later worked out and covered again. So they temporarily represent the old trough valley floor , with a corresponding maximum glacier thickness of well over 1000 meters in the Innsbruck area (city at 574 m above sea level).

However, recent studies suggest that the Lower Inn Valley could even have been free of ice in some of the warm phases of the Würm glaciation (early / middle worm, around 100,000 years ago).

Foreland ice fan (Inn-Chiemsee-Glacier)

Southeast Bavaria during the Ice Age (illustration from 1873)

In German territory, the glacier tongue pushed far out into the Bavarian Alpine foothills . The Inn Glacier also reached its greatest extent here in the Mindel glacial period and approximately as much in the Riss glaciation ( old moraines ). However, the majority of the landscape forms shaped by the Inn Glacier today come from the last Ice Age, the Würm Ice Age ( young moraines ).

Between Kiefersfelden and Brannenburg, the Inn Glacier broke through the barrier of the northern limestone Alps with the Mangfall Mountains in the west and the Chiemgau Alps in the east. Glacier cuts can be found, for example, east of the village of Fischbach ( Fischbacher Gletscherschliff ) with scratches , pits and round humps .

In the course of the successive ice ages, the glacier tongue dug a huge trunk basin into the soft rocks of the pre-alpine molasse , the Rosenheim basin . After the Ice Age, the Rosenheim basin filled with the water of the Inn, which was dammed back by the terminal moraine walls, creating the largest stem basin lake north of the Alps, the Rosenheim lake with an average water level of approx. 500 m. About 8000 years ago the water broke through the terminal moraine walls north of Wasserburg am Inn . In Wasserburg, the Inn sank deep into the layers of the Upper Freshwater Molasse, and the lake ran out completely. Even during its geologically brief post-glacial existence, the Rosenheimer See was partially filled in by the debris from the Inn. The erosion horizon of the scraper and the ground moraines on top of it lie up to several hundred meters below the current soil surface (greatest depth at the edge of the Alps, ascending to the north). Therefore, in the area of ​​the basin, sea deposits such. B. Sea clays , and not ground moraines, are the starting material for soil development. Extensive moorland areas between Raubling , Bad Aibling and Bad Feilnbach , the clay mining and the former brick production in Kolbermoor and the relatively flat landscape are based on the origin of a former lake bed.

The Inn glacier left behind large terminal moraines that can still be seen today. A very well-known terminal moraine is the Irschenberg . The exact boundary between the actual Inn glacier and the one to the east from the Tyrolean Achental is still under discussion, which is why the foreland praise is referred to as an Inn-Chiemsee glacier .

Tributaries and branch glaciers

While the foothills of the Alps were extensively glaciated up to the higher peaks, several glacier tongues can be identified which branched off from the Inn valley through main valleys to the north and formed other foothills through further alpine gates.

  • The western tongue of the Isar-Loisach glacier pushed over today's Fernpass and formed the Ammersee tongue over the alpine gate of today's Loisach Valley near Garmisch-Partenkirchen .
  • The eastern tongue of the Isar-Loisach glacier advanced over the Seefeld saddle , as shown by an ice surface at 2200 m. It split up in the Walchensee area and formed the Starnberger Tongue and the Wolfratshauser Tongue over the main basin of the Kochelsee , and over the Jachenau the upper Isar Valley and the Tölzer Tongue .
  • To the west of the Rofan Mountains, the Tegernsee Glacier advanced north, excavated the Achensee - here it was probably up to 5 km wide and 1000 m thick - and created the tongue basins of the Tegernsee and Schliersee lakes . Their meltwater washed out the Mangfall and Schlierach valleys .

At the time of maximum freezing, the ice height at Kufstein was approx. 1700 m. At the exit of the Inn valley at Ebbs , a partial stream branched off to the east.

The melting phases in the foreland

The ice edge layers of the melting phases of the Würm Glacial shape the foreland and can be easily recognized in the terrain. Carl Troll named the terminal moraine seasons after nearby locations. In some places there are further subdivisions into old and young.

literature

Main power:

  • René Hantke: Ice Age - Cold / Warm Age Cycles and Ice Transport in the Alpine and Pre-Alpine Region. Ott Verlag 2011, ISBN 3-7225-0121-0 , especially Chapter 12 Inn-Gletscher , pp. 435-460 ( content and introduction , pdf, ott-verlag.ch).

Foreland glacier:

  • Carl Troll : The diluvial Inn-Chiemsee glacier. The geographical picture of a typical Alpine foothills glacier. 1924.
  • Robert Darga: On the trail of the Inn-Chiemsee glacier . Volumes 26 and 27 of the series Walks in the History of the Earth : Part 1 - Overview , Arrow 2009, ISBN 978-3899371031 ; Part 2 - Excursions , Pfeil 2009, ISBN 978-3899371048 .

References and comments

  1. ↑ Subcommission for European Quaternary Stratigraphy, SEQS; Chaline / Jerz 1984.
  2. ↑ a b c d e f g h i j k Günter Krewedl: The vegetation of wet locations in the Inn Valley between Telfs and Wörgl. Basics for the protection of threatened habitats . (= Reports of the Natural Science and Medical Association in Innsbruck , Supplementum 9), Wagner University Publishing, Innsbruck 1992, Chapter 2.5 The Inn Glacier in the Study Area , p. 15 f ( PDF on ZOBODAT , p. 25 f).
  3. ↑ a b c d e f g It should be noted that the uplift of the Alps through folding and weight relief after the Ice Ages is still 1–2 mm / year despite erosion. In the Mindel time, the Central Alps were perhaps up to 1,000 meters lower, perhaps only a few hundred.
  4. ^ A b Christian Tarnuzzer: Geological overview of Graubünden. Reprint from: Supplement tape for the club guide through the Graubünden Alps. Chur, 1916. (Club guide of the Swiss Alpine Club) , pp. 46–52 ( pdf , burgenverein-untervaz.ch).
  5. ^ Office for Forest Graubünden: Glaciers and Climate Change in Graubünden. Fact sheet 14, January 2009, p. 4 ( pdf , gr.ch).
  6. ^ Georg Mutschlechner: In the footsteps of the Inn glacier in the area of ​​the Karwendel Mountains. In: Yearbook of Geol. Reichsanstalt 93, Vienna 1943, pp. 155–206 ( pdf , landesmuseum.at).
  7. ↑ a b J.M. Reitner: The Inn glacier system during the Würm Glacial . In: Alfred Gruber (Red.): Working conference of the Federal Geological Institute 2011 - sheet 88 Achenkirch. ISBN 978-3-85316-059-6 , articles, pp. 79-88 ( pdf , geologie.ac.at).
  8. ↑ a b Hans Bobek: The more recent history of the Inntalterrasse and the retreat of the last glaciation in the Inntal. In: Yearbook of the Federal Geological Institute 85, Vienna 1935, pp. 135–189 ( pdf , landesmuseum.at);
    Presentation follows R. Oberhauser, FK Bauer: The Geological Structure of Austria. Springer, 1980, ISBN 3-211-81556-2 , chapter 3.13.2.2. The Tyrolean Inn Valley. P. 490 col. 2 ff.
  9. ↑ Hanns Kerschner: Glaciers and Climate in the Alpine Late Glacial and Early Holocene. In: alpine space - man & environment , Vol. 6: Klimawandel in Österreich , innsbruck university press 2009, ISBN 978-3-902571-89-2 , pp. 5–36 ( pdf , uibk.ac.at).
  10. ↑ Hermann Jerz: Bavaria. In: Leopold Benda (ed.): The Quaternary of Germany. Bornträeger. Berlin 1995, p. 300.
  11. ↑ Roderich Henry, Norbert Rudolph: Genetic-chronological studies in the northern area of ​​the Inn-Chiemseegletscher. In: Ice Age and Present 28, Öhringen / Württ. 1978, pp. 83–91 ( pdf ( memento of the original from April 2, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this note. , Quaternary -science.publiss.net). @1@ 2Template: Webachiv / IABot / quaternary-science.publiss.net
  12. ↑ cf. Klaus Hormann: A new model of the Würmzeit Inn-Chiemsee glacier: thrusting of the Inn glacier over the Tyrolean Achen glacier into areas of today's Chiemsee. In: Eiszeitalter und Gegenwart Volume 25 (1974), pp. 35–47 ( pdf ( Memento of the original from March 5, 2016 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link accordingly Instructions and then remove this notice. , Quaternary-science.publiss.net). @1@ 2Template: Webachiv / IABot / quaternary-science.publiss.net
  13. ^ Rolf KF Meyer, Hermann Schmidt-Kaler: Walks in 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 . Pp. 9-14.
  14. ↑ The Fernpass was only created by a landslide after the last cold period around 4,100 years ago . He sealed off the Ehrwalder Basin , which originally leaned towards the Inn, to the south. Since then, the basin has been draining north via the Loisach.
  15. ↑ Robert Darga: On the trail of the Inn-Chiemsee glacier . Volumes 26 and 27 of the series Walks in the History of the Earth: Part 1 - Overview, Arrow 2009, ISBN 978-3899371031 ; Part 2 - Excursions, Pfeil 2009, ISBN 978-3899371048 .
  16. ↑ Carl Troll: The diluvial Inn-Chiemsee-Glacier: The geographical picture of a typical Alpine foothills glacier . Research on German regional and national studies; Volume 23, Issue 1; 1924