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A meltwater channel (or sometimes a glacial meltwater channel) is a channel cut into ice, bedrock or unconsolidated deposits by the flow of water derived from the melting of a glacier or ice-sheet. [1] The channel may form on the surface of, within, beneath, along the margins of or downstream from the ice mass.
A glacier stream is a channelized area that is formed by a glacier in which liquid water accumulates and flows. [1] Glacial streams are also commonly referred to as "glacier stream" or/and "glacial meltwater stream". The movement of the water is influenced and directed by gravity and the melting of ice. [1]
The valley wall prevents meltwater streams from flowing outward away from the glacial snout. Instead, glacial meltwater is diverted laterally along the ice margin and deposits sediments between the glacier and valley wall. [25] As the glacier retreats, the process may repeat creating a stepped slope or terrace referred to as a kame terrace.
Meltwater provides drinking water for a large proportion of the world's population, as well as providing water for irrigation and hydroelectric plants. This meltwater can originate from seasonal snowfall, or from the melting of more permanent glaciers. Climate change threatens the precipitation of snow [1] and the shrinking volume of glaciers. [2]
[1] [2] They can be up to 10 meters wide and are typically found on ice sheets and flat areas of a glacier in a region of transverse crevasses. Moulins can reach the bottom of the glacier, hundreds of meters deep, [3] [4] [5] or may only reach the depth of common crevasse formation (about 10–40 m) where the stream flows englacially. [6]
Meltwater may flow either above the glacier (supraglacially), below the glacier (subglacially/basally) or as groundwater in an aquifer below the glacier as a result of the hydraulic transmissivity of the subsoil under the glacier. If the rate of production exceeds the rate of loss through the aquifer, then water will collect in surface or ...
This process can make the existing terminal moraine far larger than its previous size. [2] Dump moraines occur when rock, sediment, and debris, which accumulate at the top surface of the glacier, either slide, fall, or flow off of the snout of the glacier. The accumulation of till will form a terminal moraine as the glacier retreats. [2]
Tunnel valleys represent a substantial fraction of all meltwater drainage from glaciers. Meltwater drainage influences the flow of glacial ice, which is important in understanding of the duration of glacial–interglacial periods, and aids in identifying glacial cyclicity, a problem that is important to palaeoenvironmental investigations. [4]