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Greenland ice sheet as seen from space. An ice sheet is a body of ice which covers a land area of continental size - meaning that it exceeds 50,000 km 2. [4] The currently existing two ice sheets in Greenland and Antarctica have a much greater area than this minimum definition, measuring at 1.7 million km 2 and 14 million km 2, respectively.
[8] [9] Ice from continental sheets is drained into the ocean by a complex network of ice streams, and their activity is greatly affected by oceanic and atmospheric processes. [8] They feature a higher velocity in the centre of the stream, and are bounded by slow-moving ice on either side. [ 10 ]
Ice caps have an area less than 50,000 km 2 (19,000 sq mi) by definition. Glacial bodies larger than 50,000 km 2 (19,000 sq mi) are called ice sheets or continental glaciers. [15] Several kilometers deep, they obscure the underlying topography. Only nunataks protrude from their surfaces.
The Antarctic ice sheet is a continental glacier covering 98% of the Antarctic continent, with an area of 14 million square kilometres (5.4 million square miles) and an average thickness of over 2 kilometres (1.2 mi).
At its eastern end the Cordilleran ice sheet merged with the Laurentide Ice Sheet at the Continental Divide, forming an area of ice that contained one and a half times as much water as the Antarctic ice sheet does today. The ice sheet faded north of the Alaska Range because the climate was too dry to form glaciers. [citation needed]
The ice sheets at the last glacial maximum were so massive that global sea level fell by about 120 metres. Thus continental shelves were exposed and many islands became connected with the continents through dry land. This was the case between the British Isles and Europe , or between Taiwan, the Indonesian islands and Asia .
The major effects of the Quaternary glaciation have been the continental erosion of land and the deposition of material; the modification of river systems; the formation of millions of lakes, including the development of pluvial lakes far from the ice margins; changes in sea level; the isostatic adjustment of the Earth's crust; flooding; and ...
Ice fields are formed by a large accumulation of snow which, through years of compression and freezing, turns into ice. Because of the susceptibility of ice to gravity, ice fields usually form over large areas that are basins or atop plateaus, thus allowing a continuum of ice to form over the landscape uninterrupted by glacial channels.