High Altitude Landscape Evolution in the Himalaya – Creating the 9000ers?

Tuesday, 16 December 2014
Simon H Brocklehurst, University of Manchester, Manchester, M13, United Kingdom and Timothy R Davies, University of Canterbury, Christchurch, New Zealand
Landscapes of the High Himalaya are broadly characterised by glacial valleys and steep, tall bedrock hillslopes, with the highest peaks represented by glacial horns surrounded by cirques. Himalayan glaciers are noteworthy for the high contribution of avalanching snow to their mass balance, and the thickness of surface debris derived from periglacial hillslopes. However, many glaciers here also do not conform to the typical case of ice accumulating in a cirque and spilling out to form a valley glacier. These exceptions include “beheaded” glaciers lacking cirques at their heads (e.g., the Barun Glacier), and “reconstituted” glaciers whose upper and lower portions are separated by bare rock slopes (e.g., the Langshisha and Yebokangal glaciers). In extreme cases these features can combine to form isolated, low-relief, ice-covered surfaces far above the rest of the glacial valley network (e.g., the Sakyetang Glacier, >6,600m, above the Kazhen Glacier, <5,400m). Such low-relief surfaces could be a key component of topographic evolution in the High Himalaya.

The ice on low-relief surfaces > 6,000m will be frozen to the bed and move very slowly. Thus subglacial erosion rates will also be very low, and outpaced by both rock uplift and rockwall retreat. Given ongoing tectonic uplift, these low-relief surfaces will continue to rise to higher elevations, raising the possibility that remnants of low-relief surfaces may end up as high as, or even higher than, current glacial horns.