Geography 323 -- Geomorphology

Glacial Processes


Distribution of glacier ice

Classification of glaciers, according to

  1. morphology

    1. niche

      • smallest glaciers
      • from in hollows, benches or from avalanche snow
      • often hanging on a cliff

    2. cirque

      • cirque have a morphology that favours the accumulation and persistence of snow and ice
      • the source of alpine valley glaciers

    3. alpine

      • valley glaciers that form when cirque glaciers advance into the valley and coalesce

    4. outlet

      • valley glaciers that radiate from an ice field

    5. transection

      • glaciers that transect drainage divides
      • ice fields, caps or sheets

    6. peidmont

      • "foot of the mountain"
      • valley glaciers which have advanced beyond the mountain front

    7. floating

      • terminus in deep water
      • e.g. margins of the Greenland and Antarctic ice sheet

    8. ice cap

      • forms a cap on a mountain range or upland, i.e. most of the peaks are under the ice

    9. ice sheet

      • continental glacier

  2. temperature: melting point decreases by 0.7o per km of ice

    1. warm- (wet-) based or temperate

      • ice is at the pressure melting point throughout the glacier
      • thus the mean annual temperature of the ice is about 0o
      • geothermal heat and melt are concentrated at the glacier bed
      • abundant meltwater and high glacier velocities from sliding

    2. cold-based or polar

      • the ice is below the pressure melting point throughout the glacier
      • that is the glacier is frozen to its bed (permafrost) and thus can move only by internal creep

    3. intermediate or subpolar

      • pressure melting point occurs only at the bed, otherwise the glacier is cold

  3. activity

    1. active

      • continuous supply of ice from the zone of accumulation
      • thus active glaciers are moving even as they waste away and retreat
      • passive

    2. undernourished

      • low velocity transfer of ice from the zone of accumulation

    3. dead

      • detached from zone of accumulation
      • usually because ice has been buried in debris or thinned out, for example, as an ice sheet advances over a topographic high
      • dead ice wastes downward as opposed to retreating from the terminus

Glacier mass balance

Glacier flow

Glen's flow law

basal shear stress

mechanisms of glacier flow

internal plastic deformation by slippage within ice crystals and recrystalization

basal sliding of temperate (wet-based) glaciers
includes regelation (melt and refreezing) around small obstacles and enhanced creep (local increase in stress and flow rate) around larger obstacles

variations in velocity

Glacial erosion and transport

erosional processes

sediment load

[ Course Outline | Next Topic ]