GEOG 2051 Chapter : 02-Apr
4/2/14
Glaciers
• Distribution
o Found in the Antarctic (mostly)
o Greenland
o High mountain elevations (less than 1%)
• Formation
o Snowline – delineates the area(elevation) at which snow can persist on a year-round
basis
o Troposphere Temperature Profile
▪ Temps tend to decrease at 6-7*C per 1000 m
▪ Snowline is lower at higher elevations
o Continental – need temps low enough so larger portion of land mass is above snowline
▪ Snow pack grows larger and larger
▪ Snow is compressed from weight of snow
▪ Welded together into firn (granulated ice crystals)
▪ Firn is compressed together to form glacial ice
▪ Takes a longer time in cold places
• Cold air cannot hold moisture
• Longer time for snow to build up
• Very little melting and melt water
o Trickles into snow pack and refreezes
• Mass Balance
o Inputs – new snow
o Outputs – melt water
o Equilibrium line = snow line ; balance between melting and new snow
▪ Accumulation zone is above snow line – where new ice is formed and added,
positive balance
▪ Ablation zone is below snow line – negative balance, ice is melting and energy is
leaving
o More melting = negative budget, losing mass and shrinking, retreating glacier
o More new ice = positive budget, larger accumulation of ice, advancing glacier
o Balanced or equilibrium budget = mass and amount of material stays constant, stagnant
▪ Glacier is still active and dynamic
▪ Ice flows from accumulation zone into ablation zone, like a conveyor belt
• Movement
o Different ice than ice in our freezers
o Structure of ice allows for glacial flow
o Brittle zone – upper-most zone, most like ice in our freezer, cracks easiest
o Plastic zone – zone below brittle zone, cannot fracture due to pressure, but it does bend
and stretch like a plastic, internal deformation – the bending (responsible for movement
of glacial ice), basal slipping – sliding of glacier across its base (movement of glacial ice),
result of presence of melt water
