GEO 101 Lecture Notes - Lecture 30: Icefall, Glacier Morphology, Basal Sliding
24 Jun 2018
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Glacier Movement
Movement of ice sheets. An ice sheet moves downslope in a number of directions
from a central area of high altitude and is not restricted to a channel or valley. The ice
sheet must expand because of the constant accumulation of ice and snow. Ice sheets
do not move as quickly as alpine glaciers because there is less slope and more mass
involved. Ice sheets move mostly by plastic flow. Mountain ranges are completely
buried by the ice sheet at the South Pole, which is greater than 3,000 meters thick.
Movement of valley glaciers.Glaciers can move more than 15 meters a day. The
larger volumes of ice on steeper slopes move more quickly than the ice on the more
gentle slopes farther down the valley. These dynamics allow a glacier to replenish the
ice that is lost in the zone of wastage. Glaciers in temperate zones tend to move the
most quickly because the ice along the base of the glacier can melt and lubricate the
surface. Other factors that affect the velocity of a glacier include the roughness of the
rock surface (friction), the amount of meltwater, and the weight of the glacier.
Basal sliding and plastic flow. A valley glacier has various components of flow. First,
the entire glacier moves as a single mass over the underlying rock surface. The
pressure from the weight of the glacier generates a layer of water that helps the ice
glacier move downslope. This process is called basal sliding.
In addition to basal sliding, which slowly moves the glacier downslope as a unit, plastic
flow causes glacial ice buried underneath more than about 50 meters to move like a
slow moving, plastic stream. The central and upper portions of a glacier, as do those ‐
portions of a stream, flow more quickly than those near the bottom and sides, where
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Document Summary
An ice sheet moves downslope in a number of directions from a central area of high altitude and is not restricted to a channel or valley. The ice sheet must expand because of the constant accumulation of ice and snow. Ice sheets do not move as quickly as alpine glaciers because there is less slope and more mass involved. Mountain ranges are completely buried by the ice sheet at the south pole, which is greater than 3,000 meters thick. Movement of valley glaciers. glaciers can move more than 15 meters a day. The larger volumes of ice on steeper slopes move more quickly than the ice on the more gentle slopes farther down the valley. These dynamics allow a glacier to replenish the ice that is lost in the zone of wastage. Glaciers in temperate zones tend to move the most quickly because the ice along the base of the glacier can melt and lubricate the surface.
