5.2: the processes that case glacier movement Flashcards
What is the fundamental cause of ice movement?
Gravity
What is the accumulation zone?
the area above the firn line, where snowfall accumulates and exceeds the losses from ablation
What is the Firn Line
A line across the glacier, from edge to edge, that marks the transition between exposed glacier ice and the snow-covered surface of a glacier
What is the ablation zone
Refers to the low-altitude area of a glacier or ice sheet below firn with a net loss in ice mass due to melting, sublimation, evaporation, ice calving, blown snow, avalanche, and any other ablation.
Describe what shear stress is
force tending to cause deformation of a material by slippage along a plane or planes parallel to the imposed stress.
Describe how a glacier moves.
Reference the accumulation zone, ablation zone, shear stress
As ice mass builds up in an accumulation zone the weight of the snow and ice exerts an increasing downslope force due to gravity - known as shear stress
Shear stress increases as the slope angle increases
Once the shear stress 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 accumulation where it eventually looses mass
Where are warm based glaciers found?
temperate maritime climates
Warm wet based glaciers experience greater snowfall in winter and more rapid ablation in the summer; therefore the imbalance between accumulation and ablation zones is …? so the glacier ice must move downslope more rapidly to maintain …? with the slope angle
- greater
- equilibrium
In cold based polar glaciers the slower the rates of accumulation, and especially ablation, result in a …? gradient of equilibrium and ..? ice movement
- smaller
- slow
Basal Sliding relates to the presence of …? beneath a glacier
meltwater
Basal sliding is movement that only applies to …? based glaciers?
warm-based glaciers
it can’t occur where the glacier is frozen to the bed
Describe the process of basal sliding
Refer to meltwater and friction in your explanation
The meltwater acts a lubricant reducing friction with both the entrained debris and underlying bedrock (this is known as slippage)
Regelation Creep (sometimes known as …?), occurs as basal ice deforms under …? when encountering obstructions such as rock steps. As a glacier moves the pressure on the basal ice will increase and it will ..?. Once the glacier had flowed over the obstruction the pressure is …? and the water refreezes
- slip
- pressure
- melt
- lowered
What base type of glaciers move by internal deformation?
And what region of the world are they found in?
Cold-based polar glaciers
internal deformation which has 2 main elements:
- Intergranular flow
- Laminar flow
Explain them both
- Intergranular flow when individual ice crystals deform and move in relation to each other
- Laminar flow when there is movement of individual layers within the glacier
