The life of the glaciers

 

Gletscherzunge am Rhonegletscher
 

The ice ages occurred during the quaternary era, the last great geological epoch, Large areas advanced were covered with ice, which advanced and retreated a number of times. In some places the ice layer was up to ten thousand feet thick. Today’s glaciers are modest remnants of those great regions of ice which, for thousands of years, determined the composition of local flora and fauna and the development of prehistoric cultures. The advance and retreat of the ice resulted in corresponding fluctuations in the levels of the seas and rivers. This is easily explains by the fact that the ice sheets and glaciers were formed principally of water that had evaporated from the oceans. Study of river and sea terraces has enables specialists to estimate the precise extent these geological events. Today it is known that an ice age was not brought about by a considerable reduction in temperatures, but by a heavy increase in precipitation. The process is very simple. It begins with heavy falls of snow on the highest peaks. The snow is exposed to a continual process of melting during the day and reversing at night, and is converted first into granular ice, or névé, and then into a compact layer of ice, from which the glacier emerges. It is fed from altitudes between about 7,00 and 8,200 ft – above the present-dey perpetual snowline which varies from region to region depending on exposure to sun and the severity of the climate. Being continually replenished from above, the glaciers move inexorably downwards, spreading out in the plains, and only stopping when the temperatures either drop to unusually low levels, or rise. the upper course of a glacier is characterised by rough of névé and frozen waterfalls .Then the gradient becomes less steep, and the glacier finally flows into the valley, the tips usually being tongue-shaped.

A glacier carries with it considerable quantities of debris which it has torn the rocks: sand, gravel, and sometimes blocks of stone of considerable size, which form the lateral, and terminal moraines. Some of the large blocks fall into transverse and longitudinal crevasse and are gradually drawn down to the ground of the glacier. Together with the moraines and the glacier itself the erode the floor of the valley. The glaciers that poured down the Alpine valleys in prehistoric times spread far out onto the plains. As They retreated they left behind them impressive erratic blocks of stone with bizarre shapes that were the source of much folklore. The glacial movements deepened and widened the valleys into lakes. Water and ice work differently. Water hollows out rock and lends the valley a V-shape. A Glacier patently removes the softer rock, but only planes and smoothes the harder rock, forming more or less deep, elegant basins; the are topped by jagged ridges interspersed with small, crystal-clear lakes. A glacier is not troubled by obstacles: it climbs over them without difficulty. It slowly but surely snakes though narrow gorges and gaps between mountain massifs, leaving characteristic scratches and furrows on the bare, rounded rock. Today the glaciers appear to be in retreat. The extent of this movement can be seen at Gletsch, where the famous hotel, once close to the tip of the Rhône glacier, is now hundred of yards below the terminal moraine. And yet periods of growth have also been observed after particularly cool and rainy summers, especially between 1920 and 1950. Nearly everywhere in the Alps the upper limit of the quaternary glaciers at the time of their greatest expansion can be seen from the sharp line dividing the high, jaggedly eroded peaks from the rocks moulded into smooth undulations by thousands of year of glacial activity.

Das alte Hotel von Gletsch
Gletsch

 

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