Factors influencing glacier ice movement Flashcards
What impact does gravity have on glacial movement?
- Glaciers flow downhill in response to the gravitational forces generated by their weight.
What is shear stress?
The build-up of ice mass over time in the accumulation zone leads to an increase in weight, increasing the downslope force due to gravity. This is known as shear stress.
How does shear stress lead to glacial movement?
Shear stress increases as the slope angle increases and, once the shear strength is great enough to overcome the resisting forces of ice strength and friction, the glacier ice pulls away and moves downward away from the zone of ablation.
The momentum of the ice’s movement towards the accumulation zone prevents further build up, thereby maintaining the glacier at a state of equilibrium with the slope angle.
Does the forward movement of glacial ice towards the snout occur in all glaciers?
The forward movement of glacial ice towards the snout of the glacier occurs regardless of whether the glacier as a whole is advancing or receding.
What does the speed of glacier movement forward depend upon?
The speed of glacier movement forward depends upon the degree imbalance between the zone of accumulation and the zone of ablation which varies according to the thermal regime of the glacier.
Which type of glaciers move the quickest?
In general, temperate (warm based glaciers) and polythermal glaciers move at greater velocities than polar (cold based) glaciers.
Why do warm based glaciers and polythermal glaciers move at greater velocities than cold based glaciers?
Glacier ice is warmer in temperate and polythermal glaciers and so deforms more easily and due to the presence of meltwater which induces basal sliding.
Why do thick glaciers often flow faster than thin glaciers?
The pressure generated by the weight of a glacier causes ice to deform and/or slide, therefore thick glaciers often flow faster than thin glaciers.
What does glacier thickness influence?
Glacier thickness influences the pressure melting point of ice.
How does the bedrock influence the rate of glacier movement?
Bedrock deformation of rocks that are easily deformable , such as clay or shale, increases the rate of basal sliding.
How does the permeability of the rock influence the rate of glacier movement?
Rates of flow vary according to whether the glacier flows permeable or impermeable surfaces as percolation of water into permeable rocks reduces lubrication and therefore glacier flow.
List some additional factors which influence the rate of glacier ice movement?
- Valley geometry
- Subglacial hydrology
- The terminal environment of the ice mass (land, sea, ice shelf, sea ice)
- Mass balance
