Glacier

Large mass of flowing ice
Composed of snow, firn and ice
Glacial ice - interlocking crystals of solid H₂O
Firn - consolidated, granular transition of snow to glacial ice
Snow - crystalline precipitation

Formation of Glaciers

Build up of snow in the zone of accumulation
Ice melts in the zone of ablation
Compaction of accumulated snow results in glacial ice
- wind pack, mechanical compaction (increased pressure), recrystallization
Glaciers will only form if the amount snowfall in winter is greater than the amount of melt in summer

Glacial Movement

Ice will flow under pressure
20 meters of accumulation is necessary before flow will occur
Glaciers flow downhill and/or away from the zone of accumulation
Ice within the glacier is always flowing away from the zone of accumulation
Greatest flow velocity is in the center and at the top of the flow

Advance and Retreat

The glacier can advance or retreat
Glaciers advance if the amount of snow added in the zone of accumulation is greater than the amount of melting in the zone of accumulation
Glaciers retreat if the amount of snow added in the zone of accumulation is less than the amount of melting in the zone of accumulation

Ice Falls and Crevasses

Glacial flow will be faster over steep slopes
Ice falls develop where the glacier flows over a steep slope
Crevasses (cracks in the surface of the glacier) develop due to:
- tensional stress
- irregularities in the valley floor

Glacier Types

Alpine
Continental

Alpine Glaciers

Glaciers occurring in mountainous terrain
Three types of Alpine glaciers
- Cirque
- Valley
- Piedmont

Cirque Glaciers

Cirque - shallow, bowl-shaped depression or amphitheater that forms due to erosion at the head of the glacier
Glaciers which do not extend past the limits of the cirque are Cirque glaciers

Valley Glaciers

Elongate glaciers confined to mountain valleys
Source area is the cirque
Develop when a cirque glacier advances past the limit of the cirque

Piedmont Glacier

Forms when multiple valley glaciers flow out of the mountains onto a broad flat plain (piedmont) and coalesce into a larger glacier

Continental Glaciers

Large, extensive ice sheets that cover all but the highest peaks of a continent
Present day continental glaciers
- Antarctica
- Greenland

Other Ice Forms

Ice Shelf - floating ice sheet that is fed by a continental glacier which flows into the ocean
Ice Pack - ice sheet which forms from the complete freezing over of an ocean
- Arctic Ocean
- does not flow like a glacier
Sea Ice - same as ice pack, but does not completely cover the ocean
- open areas between the floating ice
Icebergs - free floating chunks of glacial ice or ice sheets

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