Till

The boulder clay or Till is the sediment that is deposited directly from the glacier at its base. He is the typical sediment of the ground moraine.

Formation

Glacial ice as a solid body sorted the moving of him moraine neither the recording nor during transport. In the melting of the glacier, the material is then deposited unsorted again. Therefore boulder clay is considered diamictite and contains all particle size classes of clay over silt, sand, gravel and stones ( boulders ) to the boulders. It acts in the digestion generally massive, unsorted and unstratified. However, as a special case also stratified glacial till can be discontinued. The proportion of each grain size fractions can vary greatly, both clayey- silty and sandy or stony boulder clay before coming. It is also possible that occur with sorted sediments within the otherwise unsorted boulder clay lenses or inclusions, such as by the inclusion of the substrate. Also variable is the color of the glacial till in the digestion. While it outweigh grays, but also yellowish, reddish or bluish colors occur. The carbonate content of the glacial till derived in Northern Germany from rearranged and grated chalk, in southern Germany and Austria from the Northern Limestone Alps, in Switzerland and in France, especially from the limestones of the Helvetic.

By subsequent weathering the carbonate may be ( released) from the boulder clay washed out. The result is then non-calcareous boulder clay. Boulder also arises primarily in carbonate-free areas of origin of the glaciers, for example, in the Central Alps.

In the glaciated during the Ice Age areas of northern and southern Germany boulder clay are the most widespread deposits in addition to the meltwater sands and gravels -. They are both immediately adjacent to the earth's surface or are covered by younger deposits. Their thickness varies greatly and ranges from 0 to more than 100 meters. Moreover, they are found in all glaciated regions of the world.

From the glacial till and / or boulder clay occur in Central Europe mostly Cambisols, Lessives or related soils. They are generally fertile and valuable for agriculture. That's why most moraine in central Europe are now used as farmland.

In the technical literature has become the norm in recent years, coming from the Gaelic word Till both glacial till and for Geschiebelehme. Deposits of older ice ages, which were consolidated into solid rock, is called, however, as tillites.