Glaciers

Glaciers are a denomonation of a connecting ice mass. About a million years ago giant ice masses covered large parts of the continent and still today large "living" ice masses remain within the higher elevations on both the south and north sides of the hemispheres. Antarctica and the inland glaciers of Greenlands are a good example of these types of glaciers. Even at lower elevations there still exists great ice-currents where the higher mountain ranges act as origins for these glaciers, one example is the Baltoro glacier in Himalaya.
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Different types of glaciers

A glacier that is located in a mountain range can be mobile. The glacier "moves" from higher areas to lower terrain with the help of gravity. In combination with changes in the climate a glacier can change its appearence during a couple of decades. Differences are made between glaciers in valleys (glaciers with limited size in mountain ranges), plataeu glaciers (continues, wide stretched ice coverings over a mountain range) and interior glaciers (3-4 km thick ice which stretches across a part of a continent).

Formations

When a glacier reaches warmer climates an increased melting can cause the glacier to withdraw. More snow and ice melt at the front than what is added on the upper portions. Two types of land formations can be set free: erosion formations and accumulation formations.

Erosion formations

The best known erosion formations that have been formed by large glaciers are the tray valleys. They are u-shaped with somwhat flat bottom along with vertical walls. Their elongated profile is recognized by the mountainous thresholds and of round rock (rock that has been shaved down by ice). Another form is the nische, which is originally a small incision in the mountain where snow has been collected and compressed to form ice. The nische (which acts as the valley glaciers "origin") deepens the incision successively during thousands of years with movements in combination with frost combustion. Finally it takes shape of a rounded valley with sloped walls that are several hundred meters high.

Accumulative formations

In terms of accumulative formations, foremost we speak of the phenomenon built up of moriane. Moraine is formed when the ice moves forward and in the process draging along crushed stone and other mountainous material. Moraine is a type of soil that is recognised by the way that it is unassorted, with other words a mixture of block, rock, gravel, sand and finer materials such as clay. At the ice currents edges side-moraines are formed, in front of the glaciers end-moraines are formed along with the moraine that deposits under the glacier is called the bottom moraine.

Other common occuring formations are boulder-ridges and drumlines.

Drumlines are elongated elipse shaped backs (likes of a whale back) that form when a glacier moves across earlier deposited bottom moraines.



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