Periglacial Phenomena in Hidden Valley, Mukut Himal

Glaciological Expedition to Nepal, Contribution No. 25

Abstract

Periglacial landforms occur in the latitudinal range between the forest line and snow line in Hidden Valley and its southern outer slope. Since most of Hidden Valley is situated above the vegetation limit, sorted patterned ground and solifluction slopes cover vast areas, but vegetated patterned ground, such as earth hummocks and turf-banked terraces, is found only along the streams drained from glaciers. The occurrences of large sorted polygons and solifluction lobes are likely to be associated with the existence of permafrost. The occurrences of large sorted stripes on the supraglacial moraine seems to indicate that the glacier ice is stagnant in this part. The stripe pattern of small sorted stripes observed at 5630 m starts to become clear on gradients of more than 5° and is still clear on gradients of 40°. The rate of mass movement was proportional to the square root of the gradient of the slope and ranged from 0.4 cm/day (150 cm/year) to 0.8 cm/day, greater with one or two digits than those previously reported. Such a high rate seems to be induced by both solifluction and frost creep intensified by soaked and loose states above permafrost table, and by a steep slope angle.