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Because ice can flow faster where it is thicker, the rate of glacier-induced erosion is directly proportional to the thickness of overlying ice. Consequently, pre-glacial low hollows will be deepened and pre-existing topography will be amplified by glacial action, while nunataks , which protrude above ice sheets, barely erode at all – erosion ...
The flow of glacial ice around a boulder creates an elongated cavity in the ice downstream and parallel to its flow. The high confining pressures on the glacier bed from the weight of the overlying glacial ice fills the elongate cavity by squeezing water-soaked till into it. [1] [3] [4] [7]
Areas where the ice is most easily lifted (i.e. areas with thinner overlying ice sheets) are lifted first. Hence the water may move up the terrain underlying the glacier if it moves toward areas of lower overlying ice. [7] As water collects, additional ice is lifted until a release path is created. [8]
At the interface of the glacier and the underlying land surface, the immense weight of the glacier causes ice to melt and produces subglacial meltwater streams. These streams under immense pressure and at high velocities along with the overlying weight of the glacier itself are able to carve into landscapes and pluck sediment from the ground. [6]
Glaciologists performed a detailed radar survey of Antarctica's Gamburtsev Mountains during the International Polar Year, allowing both the overlying glacial ice thickness and the elevation of the bedrock below to be found. The survey shows overdeepening in the valley floors of up to 432 metres (1,417 ft) while the valleys exhibit steep side ...
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.
Although this ice is typically very weak (it is unable to support its own weight outside the water), it contains a lot of brine and is also relatively warm, since being that thin, its temperature is near that of the water. Rafting is accompanied with rapid draining of the brine inside the overlying ice sheet.
Till is derived from the erosion and entrainment of material by the moving ice of a glacier. It is deposited some distance down-ice to form terminal , lateral , medial and ground moraines . Till is classified into primary deposits, laid down directly by glaciers, and secondary deposits, reworked by fluvial transport and other processes.