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November 5 2014
Components of Glacier Motion
= Total Motion
Antartica has ~300 subglacier lakes as a result of geo-thermal heating.
Water at the surface - not a result of surface melting - high pressures
raise the ground water all the way up so the glacier 'floats'
Water reaches the bed through several methods - cravasses, geo-thermal
and upstream melt sources.
Pressure from subglacier water has an angled normal force which 'pushes'
the glacier down-slope.
With high pressure from glacier + sediments, the sediments break down and
also cause increased rate of movement.
Conditions of the glacier bed predomadate the characteristics of flow.
Water pressure changes
can find 'subglacier river systems'
daily fluctuations during the summer season (high at night, low in day)
increases gradually from low after summer, high by next summer.
Less sediment deformation when water pressures are high (glacier
More sediment deformation when water pressure is low (glacier 'drags')
Snow and glaciers
Distribution of snow
Annual snow line marks boundry of areas that have snow year-
The snow line varies, Lower in polar areas where temperature is
Lower in coastal areas where there is more moisture (= more snow)
Above the snow line, there are areas where snow accumulates to