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Summary Edexcel A Level Geography - Ice Movement Notes - Glaciation
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Ice movement of a glacier explained in a concise and precise way, nothing unnecessary.
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Ice Movement: Wider Reading NotesSTEPHEN HARDEN-WILSON 9/02/22
INTERNAL DEFORMATION
Slow ice creep due to slippage within and between ice crystal
Normally more significant nearer the base where pressures are higher
Occurs in temperate and polar glaciers
BASAL SLIDING
The sliding of a glacier over its rocky base
1. Basal Slip
Thin meltwater layer reduces friction and enables sliding
2. Enhanced Basal Creep
Ice squeezes up against bedrock obstacles and the pressure increases makes the ice move
around it in a plastic way
3. Regelation Flow
Same as above, but instead of behaving plastic-like, it melts and then re freezes on the other
side of the obstacle. The obstacle can’t be too big though.
BED DEFORMATION
Movement of soft rock or sediment underneath the glacier. This is more significant in temperate
glaciers because the sediment is likely to be saturated with water.
VARIATIONS IN VELOCITY OF GLACIER FLOW
Rate of movement between glaciers varies widely and this is due to…
• Thickness – higher pressure of thicker glaciers mean they move faster
• Temperature – temperate glaciers flow faster than polar ones (down to more meltwater and
ability to deform easily)
• Bedrock – the type of bedrock! Softer ones such as clay makes it easier to deform, while
impermeable rock types increase basal sliding because there is less friction sediment
• Gradient – steeper glaciers flow faster than ones that are more shallow due to increased force
of glacier
Exceptionally high rates can be caused by unique factors like an ice sheet behind ‘pushing’ the glacier.
KINEMATIC WAVES
Bulges on the surface of the glacier that are caused by increased ice accumulation (cool snowy
weather). The ice travels down the glacier as a kinematic wave, and ends up restoring the equilibrium
by evenly distributing the ice.
GLACIAL SURGES
A dramatic increase in the rate of flow of a glacier. These can cause a fast advancement of the snout.
This surge is caused by (what we think to be) a mixture of increased meltwater and therefore basal
sliding
VELOCITY
The velocity (speed and direction) of a glacier varies greatly within a single glacier.
Fastest – at the equilibrium line (thickest section of ice)
Slower movement at the top by the accumulation zone (colder and more rigid ice)
Slow rates also along lateral banks due to increased friction.
The main reason is due to compression and extensional flows (caused by steeper/ shallow gradients)
COMPRESSIVE AND EXTENSIONAL FLOW
The above mentioned steeper/ shallow differences that cause increased or decreased flows are
caused by difference in bedrock (caused by glacial erosion of the rock). In extensional flows, large
tensional cracks called crevasses are formed.
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