Glaciers as a System Revision Notes

Components of glacial systems, Energy and sediment flows through glacial systems
    → Open system - can be added to

Annual glacier mass balance

    → the annual mass balance is the difference between accumulation and ablation over     one year

    → accumulation zone = top of glacier where there is least melting, meaning there is a     positive mass balance

    → the lower section (snout) = ablation zone, negative mass balance

    → glaciers can lose mass through:

• evaporation

• sublimation

• meltwater

• calving

• avalanche

• winds 

The effect of climate on the distribution and movement of glaciers

    → Higher temperatures correlate with a faster surface velocity, as higher         temperatures mean more meltwater at the bottom of the glacier to lubricate its         movement. higher temperatures inside the ice also allow more internal         deformation

The effect of geology on rates of glacial erosion

    → weak rock types have little resistance to erosion, weathering and mm as there are         weaker bonds between particles (e.g. clay)

    → strong rock types have dense interlocking crystals so very resistant (e.g. basalt)

    → some rocks are soluble in weak acids, allowing chemical weathering (e.g. chalk)

The effect of latitude and altitudes on the distribution and movement of glaciers

    → high latitudes tend to have colder and drier climates with little seasonal variation,         leading to ice being more likely to remain for multiple seasons and therefore         eventually condense (e.g. greenland, antarctica). this is usually where cold based         glaciers form

    → high altitudes are closer to the sky, and therefore more likely to find precipitation         falling as snow instead of rain. this means there can be glaciers closer to the                  equator (e.g. the andes), due to high altitudes. this is usually where warm based         glaciers form

The effect of relief and aspect on glacier movement

    → as a glacier flows over steep slopes it cannot deform quickly enough, so stretches     and fractures forming crevasses (extending flow)

    → as the gradient of slope decreases, the ice thickens and the crevasses close due to     compression (compressing flow)

    → the steeper the relief the faster a glacier moves, evidenced by increasing crevasses     on steep relief glaciers

    → aspect (the direction the glacier faces) can impact the mass balance. if aspect is     facing away from sun, there is more accumulation, and if it faces sun there is more     ablation

Formation of glacier ice

    → glacier ice forms from low density snow fall. over time these layers of snow     compress to form layers of firn (snow that lasts through the year). This is then     pressurised, removing air from the glacier, and causing the glacier to become more     dense (glacial ice reaches densities of 0.9g/cm). This causes the glacier to look blue,     as there is a lack of oxygen. This is called diagenesis.

Types of glacier

    → constrained - smaller glaciers, limited by terrain (e.g. valley walls). valley glaciers     and corrie glaciers are constrained. tend to be smaller. often form u-shaped valleys.

    → unconstrained -larger glaciers which are able to erode surrounding landscape. ice     sheets and ice caps are unconstrained. create smoother landscapes like drumlins.

Temperature regime

    → warm based glaciers form at high altitudes, but low latitudes (e.g. alps, rockies).     the relief is steep. the basal temperature must be above pressure melting point,     causing the glacier to move relatively rapidly (20-200m a year)

    → cold based glaciers form at high latitudes (e.g. antarctica, greenland), but not     necessarily high altitudes. the relief is low. the basal temperatures are below pmp     causing no meltwater, leading to the glacier becoming frozen to the bedrock. this     causes the glacier to move extremely slowly

Glacier movement

    → gravity - causes glaciers to move down

    → gradient - steeper the slope, faster movement of ice

    → thickness of ice - influences pmp, which influences how glacier moves, and internal     deformation

    → internal ice temperature - allows for different areas of ice to move at different     speeds

    → mass balance - a positive mass balance allows advance at the snout