Sander (from Icelandic sandur ), referred to in southern Germany as gravel or crushed rock surface level, are broad, gently sloping alluvial fans that have been made in advance of the Scandinavian ice sheet or the Alpine foreland glaciers during the Ice Age. They generally consist of sands, gravels and cobbles. The term " Sander " was coined after the recognition of Glazialtheorie in the late 19th century.
As part of the Glacial series formed when glacial meltwater streams cut through the terminal moraine and widen as braided river in the plane behind it. Thus, the melt stream is greatly reduced speed and overlaid the carried material as glazifluviales sediment. The terminal moraine at the rather large slope ratio ( up to 20 ‰) decreases in the direction of meltwater runoff rapidly. Coarser material is deposited close to the terminal moraine from, whereas finer gravel and sand is still widely worn down the river, forming a characteristic landscape that is reminiscent of an inclined plane.
Dissemination and today's landscape
Sander or gravel surfaces are very common in both the North and in the südmitteleuropäischen icing area. They occur both in the Old and in the young moraine landscape. Differences between the north and the south of Germany consist mainly in the composition and grain size.
In the northern central Europe Sander is rich in sand and gravel, which is built for the most part of quartz. Therefore, the infertility of the soil stirred into the Sander areas so that they are now often used as a pine forest. Well-known examples are the Zauche south-west of Berlin, the Lüneburg Heath or the Tuchel Heath in Poland.
In the foothills of the Alps, the gravel surfaces usually consist of very coarse material ( gravel and crushed stone), which also contains a lot of limestone cobbles from the Northern Limestone Alps. The soils on the gravel surfaces are therefore not barren. Best known is the Munich gravel plain.
Examples from Iceland are the Mýrdalssandur (see Mýrdalsjökull ) or Skeiðarársandur. Crossing this Sander is not entirely without risk. By a sudden volcanic eruption under the glacier there may be tidal waves, the infamous glacier runs come.