Cloppenburg Geest
Encyclopedia
The Cloppenburg Geest is a geest
Geest (topography)
Geest is a type of slightly raised landscape that occurs in the plains of in Northern Germany, the Northern Netherlands and Denmark. It is a landscape of sandy and gravelly soils, usually mantled by a heathland vegetation, comprising glacial deposits left behind after the last ice age during the...

 region near the town of Cloppenburg
Cloppenburg
Cloppenburg is a town in Lower Saxony, Germany, capital of Cloppenburg District. It lies 38 km south-south-west of Oldenburg in the Weser-Ems region between Bremen and the Dutch border. Cloppenburg is not far from the A1, the major motorway connecting the Ruhr area to Bremen and Hamburg...

 in North Germany and the centre of the Saalian glaciation Upper Pleistocene terrain of the Ems-Hunte Geest region. The meltwater
Meltwater
Meltwater is the water released by the melting of snow or ice, including glacial ice and ice shelfs over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing...

 sands (Schmelzwassersande) of the advancing ice sheet
Ice sheet
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...

 covered the old terrain with outwash sands (Vorschüttsande). Woldstedt (1955: 159) spoke about underlying sands that, in the "Cloppenburg-Bassum Geest", belonged to the Elster glaciation. A covering of boulder clay
Boulder clay
Boulder clay, in geology, is a deposit of clay, often full of boulders, which is formed in and beneath glaciers and ice-sheets wherever they are found, but is in a special sense the typical deposit of the Glacial Period in northern Europe and North America...

 was deposited over the outwash sands during the Saale glaciation, or more precisely the Drenthe stage.

A series of meltwater valleys characterises the surface of the Cloppenburg Geest, something that was vital to the emergence of the river network. "Numerous parallel, flat channels cross the terrain and so create a landscape of parallel ridges" writes Woldstedt (1955: 158). There are two opposing theories for the formation of the rivers. Hausfeld (1983; 1984) put their emergence down to large cracks in the Drenthe ice sheet, through which meltwaters flowed as the glacier thawed, cutting through the ground moraines and down into the outwash sands. Woldstedt (1956) spoke of channels (Rinnen) in another connexion. The advancing ice followed the depth contours, conserving and deepening them. When the ice sheet retreated, dead-ice
Dead-ice
Dead-ice occurs when a glacier or ice sheet ceases to move and melts in situ. After the ice has melted it leaves behind a hummocky terrain produced by the deposition of glacio-fluvial sediments and ablation till as the ice melted. Such features include kettle holes...

 (Toteis) remained deep in these channels; it was their thawing that then enabled the rivers to flow down their old valleys.

During the marine regression
Marine regression
Marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously exposed land....

 of the Weichselian glaciation that ended about 12,000 years ago, in which the northwest German plain
North German plain
The North German Plain or Northern Lowland is one of the major geographical regions of Germany. It is the German part of the North European Plain...

 was not covered by ice, the rivers of the Cloppenburg Geest cut deeply into the valley sands. At that time the windborne and dune
Dune
In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...

 sands were formed especially as the area around the perimeter dried out.
The climate of the post-glacial period was moister and warmer. The rise in sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...

, the base level for river erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

, probably led to a rise in the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...

 in the geest depression (Roeschmann, 1971: 189). In the valleys vast fen
Fen
A fen is a type of wetland fed by mineral-rich surface water or groundwater. Fens are characterised by their water chemistry, which is neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients...

 peats formed, whilst on the valley edges and the larger basins raised bogs were formed (Hausfeld, 1983: 245).

Sources

  • Heinz-Josef Lücking: Ökologische Bewertung des Soestetals zwischen Cloppenburg und Stedingsmühlen (LK Cloppenburg, Nordwest-Deutschland) aus der Sicht des Naturschutzes unter besonderer Berücksichtigung der Vegetation, Gewässergüte und des ökomorphologischen Gewässerzustandes. BSH/NVN naturspecialREPORT 1995, ISBN 3-923788-29-0 Heft 21. Diplomarbeit im Fach Geographie an der Justus-Liebig-Universität, Gießen, 1992.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK