Ice movement in glaciers
- Created by: darcie_cl
- Created on: 25-02-14 12:55
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- Ice movement in glaciers
- GRAVITATIONAL FORCES
- Normal stresses = weight down to the ground
- Sheer stress = due to angle of slope
- Movement is driven by gravity and resisted by friction
- More movement with greater accumulation as there is greater weight
- INTERNAL DEFORMATION (ice creep)
- Slow creep of ice due to slippage within and between ice crystals - greatest at base where pressure is at its maximum
- Often creates crevasses within the glacier or at ice surface
- Type 1; INTERGRANULAR = grains slip over one another (lead shot pile)
- Type 2; INTRAGRANULAR = within a single grain of ice, stresses causes deformation along parallel lines
- BASAL SLIDING
- The sliding of a glacier over its rocky base
- Sliding is accomplished in 3 ways
- BASAL SLIP = thin layer of water builds up at ice-rock interface and the reduction in friction enables ice to slide forward
- ENHANCED BASAL CREEP = ice squeezes up against a wide bedrock obstacle, the increased pressure causes the ie to deform around the feature
- REGULATION SLIP = ice presses up to a small bedrock obstacle - ice melts and refreezes on the lee side where pressure is less
- SUBGLACIAL BED DEFORMATION
- A glacier moves over weak or unconsolidated sediment instead of hard rock
- Sediment itself can deform, moving the ice along with it
- Sediment is like jelly being forced into another area by the pressure and weight of the sliding ice
- FACTORS INFLUENCING RATE OF MOVEMENT
- Thickness of ice - thick glaciers flow slower
- Temperature of ice - warmer glaciers flow faster because they are more able to deform
- Bedrock - more rapid movement over easily deformable rocks (clay, shale)
- Gradient - steep gradients flow faster
- GRAVITATIONAL FORCES
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