What processes operate within glacial systems? Flashcards
what are some glacial inputs
precipitation
Avalanches
meltwater
rock debris
what are the glacial stores/ processes? (General)
the moving glacier erodes transports and deposits rock debris
what are the glacial outputs
meltwater
icebergs
water vapour
rock debris
what is accumulation
the input of snow and ice into a glacier
what processes cause accumulation
precipitation
wind deposits
avalanches
what is ablation
the output of snow and ice from a glacier
What are some ablation processes?
melting
ice berg calving
sublimation
evaporation
what is iceberg calving
when chunks of ice break off at the terminus, or end. of the glacier
what can cause accumulation rate to vary
high levels of inputs
low average temperatures
low levels of insolation
low wind speed
where are the highest rates of ablation
higher altitudes
on slopes with a poleward aspect
where/ what is the accumulation zone?
the uppermost section where there is greater accumulation than ablation
where/ what is the ablation zone
lower part of the glacier when the rate of ablation is higher then accumulation
what is the equilibrium line
the boundary between zones where rate of accumulation and ablation are equal
how is glacial mass balance calculated
subtracting total ablation away from total accumulation for the year
what is positive mass balance
when total accumulation exceeds ablation
what is negative mass balance
when ablation is higher than accumulation
how does the glacier move in positive mass balance
the glacier will advance as there is greater ice content
how will the glacier act when in negative mass balance
it will retreat as the input into the glacier is reduced
what will happen to the snout when in dynamic equilibrium
the glacier snout will remain stationary
what are feedback loops
deviations in in puts or outputs that move systems away from a balanced state
what do negative feedback cycles act to do?
minimise the effect of the new input, in order to re-establish stability
what is an example of a negative feedback loop
more snow in accumulation zone
increased ice volume, glacial advance
more ice volume in ablation zone
more ablation
overtime output of meltwater equals snow input
return to balance
what do positive feedback loops do?
Amplify the initial change and might cause a shift in the system to a new state of equilibrium
what is an example of a positive feedback loop (glacier)
positive mass balance
surface area increases
increased albedo
reduced air temperatures
increased accumulation
initiating positive feedback (continued advance)
how fast does the Jakobshavn glacier moving
20 meters per day at its snout
what affects glacial movement
temperature of ice
if PMP is satisfied
what happens to the melting point of ice with increased depth of a glacier
the temperature will be fractionally lowered due to the pressure of the overlying ice
what does the meltwater do on temperate glaciers
acts as a lubricant between the rock and the ice allowing the glacier to move
what is the process where meltwater acts as a lubricant for the ice
Basal slip
what glacier does basal slip happen at
most temperate glaciers
why cant PMP be satisfied in polar glaciers
Too cold to produce melt water
what happens between the bedrock and a polar glacier
the ice is frozen to the bedrock
movement only occurs by internal deformation
what is internal deformation
gravity and the pressure of the ice in the accumulation zone cause ice crystals to slide over each other in a series of parallel planes in a ‘crumpling deformation’
what can internal deformation form
deep crevasses at the surface
what factors control the rate of glacial movement
ice temperature
rate of ablation
ice thickness
precipitation levels
bedrock permeability
ice and slope gradient
how does ice temperature influence movement
colder ice moves more slowly as it does not deform as easily and stays stuck to the bedrock more
how does rate of ablation affect movement
The more melt water there id the faster the movement as basal slippage increases
how does ice thickness affect ice glacier movement
when the ice is 50m thick plastic flow begins.
the grater the thickness the greater the pressure causing faster movement (more melt water)
how does precipitation level affect glacial movement
higher snowfall leads to greater accumulation and faster movement
how does bedrock permeability affect glacial movement
if the bedrock is permeable, then meltwater may be able to soak away slowing the glacier
what is the process of water soaking into rocks
percolation
will movement be slow or quick over clay
quick as clay is deformable
how does ice and slope gradient affect movement
the steeper the slope the faster the movement due to gravity
what type of glacier is Briksdalbreen
a temperate/ warm based glacier
what ice cap feeds the Briksdalsbreen glacier
Jostedalsbreen ice cap
what is the altitude range for the brikdalsbreen glacier
1910m to 350m
what erosional processes take place in a glacial environment
frost shattering
abrasion
plucking
fracture/traction
dilation
meltwater erosion
What are the 3 areas in a glacier where material is transported
Sub-glacially
En-glacially
Supra-glacially
Where does deposition occur in a glacier?
At the snout
Where surrounding ice sublimates
Friction against the base
What is a relict glacial landscape
A area not currently glacially active but features fossilised glacial landforms due to past glacial activity
What are macro-scale landforms? (definition)
Large scale landforms that have been created by a combination of glacial processes over time
What is an example of a macro scale landform
Cirques
Arêtes
Pyramidal peaks
Terminal moraines
(Ice sheet eroded landscapes- all features combined)
What are meso-scale landforms
Intermediate scale landforms that have been created mostly by erosion but can also be created by meltwater erosion
What are some examples of meso-scale landforms
Roches moutonnes
Drumlins
Kames
Eskers
Kettle holes (fluvioglacial landform)
What are micro-scale landforms? (Definition)
Small scale landforms in some cases quite small in size
What are some examples of micro-scale landforms
Striations
Chatter marks
Erratics
What are the 4 main glacial environments we need to know about?
Subglacial
Ice marginal
Proglacial
Periglacial
What is the subglacial environment
The environment beneath the glacier ice subject to immerse pressure from the overlying ice
What is the ice marginal environment
Environment at the edge of the glacial ice where a combination of a glacial and fluvioglacial processes take place
What is a proglacial environment
Located at the front of the glacier, ice cap or ice sheet dominated by fluvioglacial activity
What is a Periglacial environment
Environment found near the glaciers dominated by freeze thaw activity but not dominated by moving ice
What are past glacial landscapes useful for
Allows us to see exact position and extent of ice cover
This process is called inversion modelling
what processes of glacial erosion are there
plucking
crushing
abrasion
fluvio-glacial erosion
What is frost heave?
Physical weathering process involving the cyclic freezing and thawing of water in soil or rock
Heave is the upward movement of the ground due to ice crystal/lenses in the soil
