(1) glaciated landscapes as systems

• what is a glacier


  a mass of ice, irrespective of size, derived largely from snow and continuously moving from higher to lower ground
• what are the inputs of a glacier


  precipitation

  meltwater

  debris

  heat
• what are the stores in a glacier


  snow

  ice

  debris

  meltwater
• what are the outputs of a glacier


  water vapour

  debris

  heat

  meltwater
• what is the accumulation zone


  near the source, where inputs generally exceed outputs
• what is accumulation


  the net gain in an ice mass
• why does accumulation occur


  more precipitation at high altitudes

  new snow is reflective and melts easily in the sun

  strong winds blow snow into hollows

  sublimation due to cold temperatures
• what is sublimation


  a trasnition into the solid state to gas with no intermediate liquid stage
• what is the ablation zone


  towards the snout where outputs exceed inputs
• why does ablation occur


  lower altitudes

  less snowfall

  higher temperatures
• what is ablation


  the process of wastage of snow or ice, especially by melting
• what is the equilibrium line


  the diving line between the two zones

  gravity moves ice continually down to the equilibrium line, replacing that lost at the snout by ablation
• what is glacial budget/net balance


  the difference between the total accumulation and total ablation for the whole of the glacier over a year
• what is the glacial budget in summer and why


  negative, increased ablation due to higher temperatures and it retreats
• what is the glacial budget in winter and why


  positive, increased accumulation due to increased snowfall and it moves forwards
• what is a steady state


  when the amount of accumulation and ablation are equal over the course of a year, therefore the glacier remains stationary
• what is glacial surge/advance


  where snowfall is exceptionally heavy, the glacier may react quickly and surge forwards
• how fast do glaciers move


  extremely variable

  fastest parts between 50m and 400m a year
• what is glacial retreat


  where the snout retreats backwards because there is more ablation than accumulation of material