Ice Formation and Glacier Movement
Diagenesis
Form when temperatures are low enough for ice to stay frozen throughout the year.
Fresh snow has a density of about 0.05 g/cm3.**
Air is expelled as each new layer of snow falls compressing it into high density ice.
Glacial ice may take between 30-1000 year to develop and it has a density of around 0.83-0.91 g/cm3.
True glacial ice is around 100m down and it is slightly blue not white.
Valley Glaciers
Follow the course of existing river valleys so confined by valley sides.
May be outlet glaciers from ice sheets or fed into by corrie glaciers.
Typically 10-30km in length.
E.g. Alps, Himalayas, Rockies, Andes.
Ice Sheets
Accumulations of ice extending more than 50,000km2.
Possess 96% of the world's ice.
Huge ice sheets covered most of Europe in the last glacial period.
Only found in Greenland and Antarctica (ice up to 4700m thick) today.
Warm-based Temperate Glaciers
Cold-based Polar Glaciers
High rates of accumulation and ablation.
Limited rates of accumulation and ablation due low precipitation and temperatures below 0ºc.
Basal temperatures at/near pressure melting point.
Meltwater created due to pressure melting at the base of the glacier.
Rapid movement - mobile glacier, able to carry out erosion producing glacio-fluvial , erosional landforms.
Move by basal slippage (regelation slip, creep etc.).
Basal temperatures below PMP so no basal slippage as no meltwater.
Slow rates of movement due to low temps. Move by internal deformation.
E.g. Antarctica, Greenland.
E.g. Alps, Rockies.