page_title: Seerhein
section_title: Paleogeographic Development
hierarchical_section_title: Seerhein / Paleogeographic Development
caption_attribution_description: Français&#160;: Glacier Perito Moreno, situé dans le Parc national Los Glaciares au sud de l'Argentine English: Perito Moreno Glacier, in Los Glaciares National Park, southern Argentina Español: Glaciar Perito Moreno, en el Parque nacional Los Glaciares, sur de Argentina Italiano: Ghiacciaio Perito Moreno, nel Parco nazionale Los Glaciares, sud Argentina 中文: 莫雷诺冰川，位于阿根廷的冰川国家公园。
context_page_description: The Seerhein is a river about four kilometres long, in the basin of Lake Constance. It is the outflow of the Upper Lake Constance and the main tributary of the Lower Lake Constance. The water level of the lower lake is about 30 cm below the level of the Upper Lake. It is considered part of the Rhine, which flows into Lake Constance as the Alpine Rhine and flows out of the Lake as the High Rhine. The Seerhein arose after the last Ice Age. Some time after this period, the water level of Lake Constance gradually dropped by about ten metres and the shallow parts fell dry. Some parts of the Seerhein still have a character a bit like a lake.
  The border between Germany and Switzerland runs down the center of the lower stretch of the river; the German city of Constance, the largest community on the river, is situated on both sides of the upper part.
context_section_description: The entire landscape of the Seerhein and its environment is in the range of Molasse basin, which was formed during the Upper Miocene about 30 million years ago.  In the next 7 million years (until now) the sedimentation exceeded the erosion.  During this timeframe, the present landscape was formed.  During the Pliocene and Pleistocene, erosion was dominated by the Aare and Danube, later by the High Rhine.  Rivers and glaciers created furrows and basins.
  The paleogeographic development of the Seerhein is closely connected to that of the valley through which it flows.  This valley was created by the early High Rhine and the Rhine glacier and filled by different lake deposits.  The entire Lake basin is characterized by the alternation of the wide basin, narrow cross valleys and mountainous landscapes.  The lowlands surrounding the Seerhein are largely the result of siltation and is one of the basin landscapes; the neighbouring hill ranges Bodanrück and Seerücken are glacial molasses highlands.
  A decisive step in the formation of today's Seerhein and Lake Constance area took place with the deflection of the Alpine Rhine from the Danube to the Aar during Günz ice age.  On the line Lake Constance-Seerhein-High Rhine enhanced vertical erosion followed, while the advancing Rhine glacier prepared today's Lake basin.
  The retreat of the Rhine glacier (at the end of the Würm ice age) occurred as a number of melting and stationary phases, which are conventionally divided into nine stages.  Stage 9, the "Constance" stage, begins with the edge of the ice at a standstill near Constance.  The ice edge east of the glacier was along a line from the Lake Überlingen via the eastern tip of Bodanrück, through Constance and Kreuzlingen to the northern end of the Seerücken.
  Early in the Constance stage, a proglacial lake formed in the area of today's Seerhein basin and to the west of it.  In this lake, extensive silty calcareous, glacilimnic layers were deposited.  These appear on the surface in some places on the edge of the valley.  After the Ice lake disappeared, a terminal moraine was formed, which later turned out to be important for the course of human settlement (see below).  Initially, the melt water from the Lake Überlingen basin flowed through Staringen Valley; later it flowed through the Allmannsdorf melt water channel in the area of today's Seerhein depression. A melt period followed, in which all ice in the Konstanzer Trichter and Obersee melted.
  After the end of the Würm Ice Age (about 9650 BC) the water level of Lake Constance was at about 405 m above the current sea level, or about 10 metres above the present level.  Back then, the Seerhein valley was submerged and Lake Constance was a single lake.  Deep erosion of the Rhine then lowered the lake to its current level (about 395 m).  The Seerhein valley fell dry; the Upper and Lower were Lake separated, and the Seerhein emerged as the connection between the two lakes.  The course of the present Seerhein may well correspond to the location of the current in the days when Lake Constance was a single lake.  The former extent of the lake is indicated by typical lake deposits; in the Seerhein valley, such deposits are found all over the valley floor.  These lake sediments usually have a thickness of 0.2 to 2 metres, near the Seerhein up to 13 metres.  In the western part of today's depression, the surf of the lake formed many beach ridges perpendicular to the main wind direction (southwest); ridges in the Wollmatinger Ried are still well preserved.  Besides the described main elements (Würm moraine, Ice Lake sediments, Lake deposits, including the beach ridges), Pleistocene talus and Holocene alluvial fan are found in Seerhein basin.
caption: Glacier with Ice Lake (Perito Moreno Glacier, Argentina)
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