glacial movement Flashcards
extesional flow
at the head of the glacier, the valley is steep so there is a strong gravitational force pulling the ice downwards
when the ice moves quickly there is more tension
this causes the ice to fracture into thick layers, which can slip downwards
compressional flow
lower down in the glacier, ice is moving more slowly because the valley is less steep
the faster ice from the head of the glacier pushes down on the slower ice and compresses it
the high pressure causes the ice to fracture into layers and the layers slip forward
faster moving ice is found…
- on steeper slops
- at the base of the glacier
- be a part of a larger glacier
- be temperate (warm bases)
- moving over impermiable bedrock
- be found in narrow valleys
positive feedback loop
if the glacier has a large volume of meltwater, it will move relatively quickly due to basal slip.
this will generate greater levels of heat due to friction and the heat will further increase the meltwater, therefore the speed the glacier moves
negative feedback loop
a fast moving glacier will become thinner as the amount of meltwater increases
this thinning eill eventually slow the glacier down, as less pressure will be exterted on the base og the glacier which means less meltwater would be produced
slope
- if a glacier is on a steep slope, its weight will have more of an impact on its movement. this is because the force exerted downslope is stronger than the friction holding it in place
- this means that glaciers on steep valley slopes will move much faster than those on flat valley floors
temperature
the degree to which a glacier moves depends on its melting point
- the surface of the glacier will have a melting point at 0ºC.
- at greater depths within the glacier the melting point will be lower
- this is due to the increased pressure from the ice above
-the ise within the glacer will flow at a faster rate than at the surface
how do
temperatures in polar regions
affect the movement of glaciers
in polar regions where temperatures are very lowm they are more likely to be cold based and more likely to freeze to the bedrock and move more slowly due to the absense of meltwater
size
the larger the glacier, the greater the pressire on the base of the glacier and the easier the ice will melt.
this creates a faster moving glacier
altitude
high altitude glaciers
glaciers at higher altitudes are more likely to experience greater levels of precipitation which lead to hugher rates of accumulation and have a positive mass balance.
this means that the glacier will be able to advance and move mofre quickly. however at high altitudes the glacier is likely to freeze to the bed and slow down the glacier
altitude
lower altitfute
temperatetues are warmer at lower altitudes. this means glaciers are likely to undergo melthing at the base of the glacier which can increase basal slip and cause the rate of the glacier movement to increase
altitude
temperate glaciers
temperate glaciers are likely to be found at lower altitudes or sea level.
the sounts ofsome of the glaciers can move faster at up to 10 a day. this may be due to a glacial surge
glacial surge
where the snout moces very quickly due to instability within the end of the glacier
lithology
permeable
a permeable bed rock will soak up some of the meltwater at the base of the glacier, reducing the glaciers ability to moce
lithology
impermiable
glaciers on top of impermeable rock will move faster because of increased meltwater which reduces friction
