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Glaciers - part 1
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The name glacier has been applied to ice bodies varying from small residual glaciers in Colorado, moving a few inches a year, to a valley glacier in Greenland which races along at 99 feet per day. Few are the mountains really deserving of the name that have not been severely modified, and made beautiful, by glaciers. Even the ski mountaineer who never expects to see glaciers would do well to know a little of them so that at least he can recognize their effect on the mountains he travels.
Wherever more snow accumulates every year than can melt in place, it forms permanent snowfields (neve), compacts into ice, breaks away from the mountain (at the bergschrund), and flows slowly downhill. Irregularities in its course may break the surface into roughly parallel cracks (crevasses), confluence with other glaciers may buckle it (pressure areas), and the glacier bed may break it up badly (icefalls with their ice-block seracs), or drop it over cliffs (hanging glaciers). Tributary glaciers may join it, either by means of icefalls, by dropping from hanging glaciers, or by simple confluence, and a lake of ice may form (icefield), from which the main glacier descends far below the peaks (valley glacier). On its surface will be the sand and rock debris that has avalanched from the mountains (lateral moraines at the sides, medial moraines down the middle, formed of lateral moraines where two glaciers join), and which is piled up where melting equals the flow, at the end of the glacier (terminal moraine at the terminus or snout). Also on the surface is the surface-drainage system, consisting of ice marshes, of small lakes in pinched crevasses, streams and waterfalls that finally disappear in crevasses or glacier mills (moulins), to join the main stream that flows beneath the glacier or subsidiary streams along the sides. Where the glacier flows past cliffs the edge will be melted back (the moat, or randkluft). But the ski mountaineer ascending a mountain will meet these features in reverse order. Certain considerations should be given each: The terminus.—This may be so covered with morainal material—even forest and lakes in Alaska—as not to be recognizable. During the present climatic cycle, however, most glaciers have retreated far, and are approached by rock-strewn valleys which forests have not yet had time to claim. The terminus may be an abrupt ice cliff that the climber will have to cut his way up, or may even thrust itself into a fjord, with icebergs being launched at irregular intervals. Moat and moraine.—A moat may have to be reckoned with if the glacier is approached from the side. Steps may have to be cut, but usually a bridge of debris from a side canyon will provide easier access. Moraines provide a hazard only in their instability. Melting ice leaves many of the blocks precariously perched. When disturbed, they may roll on the man who is following the disturber too closely. Valley glacier.—A smooth valley glacier is the best avenue of approach to a heavily glaciated region. In 1942 the United States Army's Columbia Icefield Detachment used such a glacier, with only slight modification, as a truck route. During most of the summer season the surface is free from snow, is granular, and provides excellent footing for nailed or Bramani-soled boots. Crevasses are easily seen, and may often be avoided altogether if the climber selects a route along the inside corners of the glacier's turns, where the crevasses are closed by pressure. The ice in the mills and surface-stream channels is very smooth, and is best avoided. The primary hazard is that of avalanche from slopes high above the glacier.
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