Moving ice, made of compacted snow
Presently hold ~2% of earth’s water
Important for:

• erosion and deposition
• part of global climate

• More snow falls than is melted.
• Snow compacts and recrystallizes to form ice.
• When thickness ~ 40 m, it begins to move

1. Valley glaciers- in mountains
2. Continental glaciers (ice sheets)
very extensive (ex. Greenland, Antarctica)
3. Ice caps
smaller than continental, can form from merging of valley glaciers (ex. Iceland)

Movement of glaciers
Plastic flow
Basal slip (due to water at base)
                   surges can occur if water builds up

Top layer of glacier (~40 m) is brittle.
crevasses (large fractures) form.

Valley Glaciers: move from higher elevation to lower elevation
Ice sheets: flow from thicker to thinner areas

Glacial Budget
In (accumulation): snow
Out (wastage): melting, sublimation, calving of icebergs

Advancing glacier: positive budget
Receding glacier: negative budget
 (Note: glacial ice continues to move forward).

Glacial erosion:
     Plucking: water freezes around sediment
     Abrasion: by sediment carried in ice at base of glacier
                striations: grooves caused by abrasion

Erosion features of valley glaciers

• Cirque: a circular depression formed at the head of a valley glacier
• Arete: knife-edged ridge that divides adjacent valleys
• Horn: formed by the walls of 3 or more cirques
• U-shaped valleys