Nunatak

Nunatak ( Inuktitut and Kalaallisut: Nunataq, majority Nunatait or Nunatakker ) referred to in glaciology an isolated, over the surface of glaciers and ice sheets towering rock or mountain. This rock is thus surrounded by a Eisstromnetz. Mostly, nunataks found at the edges of ice sheets. Less commonly, the term Nunatak but also commonly used for ice-free, surrounded by glaciers areas ( as now the Antarctic dry valleys, during the ice ages, for example, low-lying regions of Baffin Iceland and Labrador ) and not used exclusively for surveys.

Nunataks during the ice ages

The " Nunatakhypothese " assumes that in the icy during the Ice Age areas nunataks important refuge areas ( refugia ) were for many animal and plant species. These "islands" in the ice played an important role in the survival of plant species such as the sky Herold, Dolomite cinquefoil, Swiss Mannsschild or the Alps Thrift, according to this theory. Meanwhile, it is assumed that nunataks were the survival of these species of minor importance and they survived the cold periods in other places. The formerly glaciated areas were therefore from the outside completely repopulated ( " tabula rasa hypothesis "). For the development of the vegetation in northern Europe will be discussed today whether some regions on the west coast of Norway, in particular fells around the central Sognefjord and the Arctic Circle to the Finnmark could have been ice-free refugia to the existence of endemic in Norway poppy species or the local occurrence scirpoidea of species such as rhododendron lapponicum and Carex to explain their next areas are in Greenland and North America.

In addition, today this hypothesis underlying ice thickness be doubted: Attempts are often made on the basis of the tracks, the glacial glacier had left on the nunataks of them reflowed to determine the former glacial ice thickness. This method is now regarded as unreliable because, due to post-glacial weathering traces of ice in the summit regions receive only bad. Moreover, according to recent findings präglaziale weathering phenomena such as block fields that were regarded as signs of lack of glaciation long, also survive long ice cover. It must therefore be assumed that the glacial ice sheets were thicker than expected due to these symptoms and many alleged former nunataks were covered in reality entirely from ice.