Glacial Processes

Glacial Processes - basal sliding of temperate(wet-based...

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Glacial Processes Glacier flow Glen's flow law strain rate is proportional to temperature cubed (T 3 ) the behavior of glacier ice is mostly plastic; beyond a yield stress of about 1000 N/m 2 , it deforms continuously, i.e. flows under its own weight with no increase in stress but its not perfectly plastic, because it creep under low stress, i.e. like a viscous fluid basal shear stress shear stress = W sin(slope) and the density of ice is fairly constant, therefore bed shear stress is a function of the thickness and slope of the ice so glacier flow is driven by slope (mountains) or thickness (ice sheets) mechanisms of glacier flow creep internal plastic deformation by slippage within ice crystals and recrystalization
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Unformatted text preview: basal sliding of temperate (wet-based) glaciers includes regelation (melt and refreezing) around small obstacles and enhanced creep (local increase in stress and flow rate) around larger obstacles variations in velocity • high velocity in thickest ice, i.e. in the middle of the glacier and near the equilibrium line • extending flow o acceleration with increasing slope or thickness o flow lines are directed towards the bed promoting erosion o causes crevasses and, on steep slopes, ice falls • compressive flow o deceleration with decreasing slope or thickness ( e.g. the terminus) <li>flow lines are directed upward, carrying debris to the ice surface </li...
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