Glacial Processes (Edexcel A Level Geography): Flashcards
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Define glacier.
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Cards in this collection (39)
Define glacier.
A glacier is a large mass of ice that moves downhill under gravity, acting as an open system with inputs and outputs.
What is mass balance in a glacier?
Mass balance is the difference between accumulation and ablation over a year, showing whether a glacier gains, loses or maintains its ice mass.
Snow compacts into firn or before becoming glacial ice.
Snow compacts into firn or névé before becoming glacial ice.
How long can it take for glacial ice to form in polar regions?
In polar regions such as Greenland, glacial ice formation can take up to 150 years, and in Antarctica even thousands of years.
Define accumulation (in glaciology).
Accumulation is the input of mass to a glacier, mainly from snowfall, avalanches and windblown snow or debris.
Define ablation.
Ablation is the loss of ice mass from a glacier through melting, evaporation, sublimation, calving and avalanches.
The balance between accumulation and ablation over a year is the .
The balance between accumulation and ablation over a year is the glacial budget.
Where is the accumulation zone found on a glacier?
The accumulation zone is in the upper part of a glacier, where inputs exceed outputs, causing a net gain of ice and glacier advance.
True or False?
Sediment on glacier ice can create a positive feedback increasing melting.
True.
Sediment absorbs more insolation, increasing melting, which exposes more sediment and further accelerates melt rates.
What happens to a glacier in equilibrium?
In equilibrium, accumulation equals ablation, so the glacier’s overall size and front position remain unchanged over time.
Glacial health is assessed over a year period.
Glacial health is assessed over a 10 year period.
Define Greenland Ice Sheet.
The Greenland Ice Sheet is the largest ice mass in the Northern Hemisphere, covering about 80% of Greenland and storing vast freshwater ice.
How much could sea level rise if Greenland melted completely?
If the Greenland Ice Sheet melted completely, global sea level could rise by about 7.4 m, flooding many coastal areas worldwide.
True or False?
Greenland meltwater can affect thermohaline circulation.
True.
Large freshwater inputs from Greenland reduce ocean salinity and density, potentially disrupting thermohaline circulation and the Gulf Stream.
Define pressure melting point (PMP).
The pressure melting point is the temperature at which ice melts at a given pressure, lowering as pressure increases.
How do warm-based glaciers differ from cold-based glaciers in basal conditions?
Warm-based glaciers have basal ice at or above the PMP, enabling basal sliding. Cold-based glaciers stay below the PMP, so ice is frozen to bedrock and sliding is minimal.
In warm-based glaciers, basal sliding is assisted by produced during summer.
In warm-based glaciers, basal sliding is assisted by meltwater produced during summer.
In cold-based glaciers, basal temperatures remain the pressure melting point, so basal sliding does not occur.
In cold-based glaciers, basal temperatures remain below the pressure melting point, so basal sliding does not occur.
True or False?
Cold-based glaciers typically move faster than warm-based glaciers.
False.
Warm-based glaciers usually move faster because basal sliding is active, whereas cold-based glaciers mainly move by slow internal deformation.
How does slope angle affect the rate of glacier movement?
Steeper slope angles increase shear stress downslope, so glaciers on steeper gradients generally move faster than those on gentle slopes.
Define glacier surge.
A glacier surge is a short-lived period when a glacier moves 10–100 times faster than normal, rapidly advancing downslope.
Greater glacier and thickness increase internal pressure, usually leading to faster movement.
Greater glacier size and thickness increase internal pressure, usually leading to faster movement.
True or False?
Higher accumulation can increase glacier velocity.
True.
Higher accumulation thickens the ice and steepens the surface gradient, increasing shear stress and often velocity.
Define basal sliding.
Basal sliding is glacier movement where meltwater at the base lubricates the bed, allowing the ice to slide over the bedrock.
What is internal deformation in glacier ice?
Internal deformation is movement as ice crystals and layers bend and slide past each other, allowing the glacier to flow even when frozen to bedrock.
When a glacier enters a gentler slope, compressional flow makes the ice mass and increases erosional potential.
When a glacier enters a gentler slope, compressional flow makes the ice mass thicken and increases erosional potential.
Define micro-scale glacial landform.
A micro-scale glacial landform is a small feature up to about 1 m long, such as striations, grooves or chatter marks on bedrock.
Define meso-scale glacial landform.
A meso-scale glacial landform is a medium-sized feature like drumlins, ribbon lakes or roche moutonnées formed by glacier ice and meltwater.
Define macro-scale glacial landform.
A macro-scale glacial landform is a large feature such as pyramidal peaks, glacial troughs and cirques/corries/tarns that shape whole mountain landscapes.
What is process morphology in glacial landscapes?
It is how different glacial processes operating in different glacier zones create differently shaped landforms at different scales, times and places.
The zone is beneath the ice, where pressure causes grinding, scratching and polishing of bedrock.
The sub-glacial zone is beneath the ice, where pressure causes grinding, scratching and polishing of bedrock.
At the margins, both glacial and fluvio-glacial processes operate at the sides and front of the glacier.
At the glacial margins, both glacial and fluvio-glacial processes operate at the sides and front of the glacier.
True or False?
Periglacial environments are mainly controlled by ice movement.
False.
Periglacial environments are dominated by freeze-thaw and permafrost processes rather than direct ice movement.
What is an upland glacial landscape?
An upland glacial landscape is a high-altitude area of hills or mountains containing features like arêtes, corries and pyramidal peaks.
Define inversion modelling in glacial studies.
It is mapping past ice cover using present landforms and deposits to reconstruct relict glacial landscapes and former glacier extent.
landscapes are no longer influenced by ice masses, while
landscapes are still shaped by ice.
Relict landscapes are no longer influenced by ice masses, while active landscapes are still shaped by ice.
True or False?
Pingos only occur in upland glacial landscapes.
False.
Pingos are lowland periglacial features that can indicate past permafrost conditions, even in present lowland areas.
Define glacial erosion.
Glacial erosion combines abrasion, plucking, fracture and traction, dilation and meltwater erosion to wear away and reshape bedrock beneath and around glaciers.
Glacial material deposited directly by ice is , while material laid down by meltwater is .
Glacial material deposited directly by ice is till, while material laid down by meltwater is fluvio-glacial debris.
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