3. Karakoram Glaciers: Types and Terrain

This chapter focuses on the glaciers themselves, ice morphology and distribution and relations to terrain in their basins. To identify the relative extent of zones with particular conditions, criteria are outlined to define terrain elements on and off the ice. Estimates are given of their share of basin areas for the 42 largest glaciers and provide a basis for the investigation of glacier mass balance and landforms in later chapters. The importance of verticality is further reinforced. Relative distributions of perennially frozen, snow-covered areas and seasonally snow-free and thawed surfaces are underscored. These prove to be distinct from conventional glacier accumulation and ablation zones in some important respects, mainly due to complications arising from the extent of off-glacier rock walls and of snow redistribution by wind and avalanches. Icefalls, supraglacial debris mantles and ice-margin deposits are of particular interest. Glacier ice itself is shown to comprise, on average, one-third of basin areas above glacier termini and about 45 % of perennial snow and ice areas. Rock walls make up more than 65 % of the latter and 60 % of whole basin areas. Considerable differences emerge between basins, as illustrated by comparing Baltoro, Biafo and Toltar–Baltar Glaciers. They support an argument for revisiting older classifications of Karakoram Glaciers into Mustagh, Turkestan and Alpine types, which emphasise differences in nourishment, especially the relative shares of avalanche-fed ice. A fourth ‘wind-fed’ class, widely present in the region, is added. With certain revisions, these classes help to identify key conditions in the Karakoram. The four types are also distinguished by the proportions of terrain elements in their basins, notably rock walls and the extent or absence of accumulation zones. Classifications by size, morphology, climatic and thermal regimes are also examined. They raise some unique questions and reinforce a sense of the distinctiveness and diversity of ice masses in the Karakoram.