Ice as an Agent of Sculpting Land




Glaciers are formed when snow, compressed into large thickness of crystalline ice mass, develops an ability to move due to sheer mass. These glaciers together with snow and ice constitute the cryosphere which covers nearly 10 per cent of the surface of the earth (NSIDC, undated). The major part of ice and glaciers is found as ice caps and ice sheets in Arctic, Antarctic and Greenland, apart from the Himalaya, Andes and Europe. The glacierised area of the earth is spread over nearly 15 million sq km of the land surface and account for approximately 75 per cent of the freshwater resources of the world (ibid). During the Quaternary period that lasted for 2.6 million years, the earth saw many changes in its climate, forcing repeated glacial and interglacial cycles, caused by the earth’s orbital changes including the tilt of its axis (Milankovitch cycles). As evidenced by the ice cores drilled from various locations of Antarctica, such as Vostok and Dome C, the earth witnessed eight cycles of ice ages each separated by an interglacial period in its history of past 750,000 years (EPICA, 2004). During the immediate past ice maxima period (~20,000 years before present), the glaciers covered 32 per cent of the land surface and sculpted various landforms transforming the geomorphology of earth into a shape that we see today. Not far back, between 17th and late 19th century—during the period called ‘Little Ice Age’—the world saw consistently cooler temperatures that helped the glaciers advance. The advance or retreat of a glacier is seen at its snout, which may be defined as the terminus, toe, or the end of a glacier at any given point in time (Figs. 1 and 2).


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