Glacial valleys are the name given to broad valleys in Central Europe , which were formed in the ice ages or in the individual stages of an ice age on the edge of the Scandinavian inland ice or the alpine glaciation and were created by the more or less runoff of the melt water parallel to the ice edge . They belong to the glacial series .
Origin and structure
What is important in the formation of the glacial valleys is the general downward slope of the landscape in the north German lowlands and in Poland from south to north . The inland ice coming from Scandinavia pushed forward against a sloping terrain. The meltwater could only flow a short distance on the Sandern to the south and then looked for a path parallel to the edge of the ice in the direction of the North Sea basin. The area of the North Sea was dry terrain at that time due to the significantly lower sea level.
As part of the glacial series, glacial valleys interlock on their northern edge over long stretches with sand areas, through which meltwater was supplied to the glacial valley. Glacial valleys are made up of relatively uniform sand and gravel , but the grain size can fluctuate widely. Especially in the upper sections of the glacial valley sediments, finer sands dominate. The thickness of the glacial valley sediments also varies greatly, but is usually well over ten meters.
Glacial valleys have an extensive, table-level valley floor that is between 1.5 km and 20 km wide. The valley slopes, however, are only a few to a few dozen meters high. The bottom and the edges of a glacial valley can be changed significantly by recent processes, in particular by the thawing of blocks of dead ice or the blowing up of dunes . In the post-ice age , many glacial valleys are muddy due to their low location and the associated high groundwater level .
Glacial valleys in Central Europe
In Central Europe there are several glacial valleys from different periods.
- Breslau-Magdeburg-Bremen glacial valley: runs through southern Poland and Germany ; was created in the Saale Ice Age .
- Glogau-Baruther glacial valley : runs north of the Breslau-Magdeburg-Bremer glacial valley through southern Poland and Germany; was created in the Vistula Ice Age.
- Warsaw-Berlin glacial valley : formed in the Vistula Ice Age, runs through central Poland and Germany.
- Thorn-Eberswalder Urstromtal : runs through northern Poland and Germany; was created in the Vistula Ice Age.
- As Elbe glacial valley , the Elbe Valley from the height of Genthin to the Elbe estuary at Cuxhaven referred. The melt waters of the three aforementioned glacial glacial valleys flowed one after the other through this valley towards the North Sea basin.
- The name Rheinurstromtal for the Rhine valley from Düsseldorf to the confluence with the North Sea is controversial . The Rhine served as an outlet for the meltwater during the Saale Ice Age. The layout of the valley is much older and was created by young tectonics .
- In alpine glaciation areas, the gravel terraces in the glacial valley of the Danube have been redesigned in various ways over the course of centuries during extreme flood events by shifting the river bed. Its large tributaries from the Alps run largely in their glacial valleys and form the typical terraces.
Sections of the main valleys have been given their own names. The Lausitzer Urstromtal and the Aller-Urstromtal are sections of the Breslau-Magdeburg-Bremer Urstromtal. Baruther , Berliner and Eberswalder Urstromtal are common abbreviations for the relevant glacial valley sections in Brandenburg . In addition to the large main valleys, there are numerous smaller glacial valleys . Their appearance initially resembles the large glacial valleys. However, they are much shorter and there is no reference to a sander and a terminal moraine .
Special features of glacial valleys
Glacial valleys should not be confused with glacial gullies (tunnel valleys). The latter arose under and not in front of the ice. In addition, most of the glacial channels run from north to south. The main direction of the glacial valleys is from east to west. Rivers flow through glacial valleys only in sections, as most of them can reach the sea by shorter distances, as in the case of the Oder and Vistula . The linear depressions of the glacial valleys between the rivers were used for the construction of canals because of their low gradient, for example for the Elbe-Havel Canal or the Oder-Havel Canal .
Since the slope of the landscape in North America and on the Russian table faces south, glacial valleys did not form there during the Ice Age. The Mississippi River and its tributaries have carried away the meltwaters of the North American ice sheet. In Eastern Europe, the meltwater flowed off via the river basins of the Dnepr , Don and Volga .
Glacial valleys, whether sandy or muddy, represented considerable obstacles to traffic in the Middle Ages. Therefore, the trade routes were bundled at narrow points at which the valley could be crossed relatively easily. The bottlenecks were a preferred place for city foundations and castles. Examples in Brandenburg are Berlin , Fürstenwalde , Luckenwalde and Baruth / Mark as well as in Lower Saxony Vorsfelde and Wolfsburg Castle .
- Herbert Liedtke: The Nordic glaciations in Central Europe (= research on German regional studies. 204). 2nd, expanded edition. Central Committee for German Regional Studies, Trier 1981, ISBN 3-88143-020-2 .
- Herbert Liedtke, Joachim Marcinek (Hrsg.): Physical geography of Germany . 3rd, revised and expanded edition. Klett-Perthes, Gotha et al. 2002, ISBN 3-623-00860-5 .
- Guide to the geology of Berlin and Brandenburg. No. 2: Johannes H. Schroeder (Ed.): Bad Freienwalde - Parsteiner See. 2nd improved edition. Self-published geoscientists in Berlin and Brandenburg e. V., Berlin 1994, ISBN 3-928651-03-X .
- Guide to the geology of Berlin and Brandenburg. No. 5: Johannes H. Schroeder (Ed.): Northwestern Barnim - Eberswalder Urstromtal - Barnim Nature Park. Self-published geoscientists in Berlin and Brandenburg e. V., Berlin 2004, ISBN 3-928651-06-4 .
- Guide to the geology of Berlin and Brandenburg. No. 9: Johannes H. Schroeder, Fritz Brose (Ed.): Oderbruch - Märkische Schweiz - Eastern Barnim. Self-published geoscientists in Berlin and Brandenburg e. V., Berlin 2003, ISBN 3-928651-11-0 .
- Water Management Office Bavaria Historical Development of the Danube - accessed on April 21, 2016