Different Types of Glacier and Glacier Movement

Snow

• Flakes with open, feathery structure
• Low density (0.05 g/cm^3)

Firn/Neve

• Snow that survives a summer/whole year
• Compressed and compacted by the fresh snow fall
• Air expelled
• Density is 0.4 g/cm^3

Glacier Ice

• Further Compaction
• Diagenesis- process by which snow becomes ice due to compression. Takes as little as 30-40 years up to over 1000 years
• Density is 0.3 to 9.1 g/cm^3
• Not found until depth of 100m
• Blueish in colour

• Glacier- Large, slow moving mass of ice
• Ice Sheet- Largest Accumulation of ice (>50,000km^2 (Otherwise called an ice cap))
• There are only 2 ice sheers today (Greenland and Antarctica)
• Antarctica- 13.6 million km^2, 30 million km^3, over 4700m deep in eastern antarctica

Valley Glacier

• Confined by Valley Sides
•             EITHER outlet glacier from ice sheet/cap OR fed by snow and ice from one or more corrie glaciers
• Follow course of existing river valleys or corridors of lowland
• Typically 10-30km long- Karakoram Mountains glacier in Pakistan up to 60km

Basal Temperature

• Temperature at the base of the glacier where the ice meets the ground

Pressure Melting Point (PMP)

• Temperature at which ice is on the verge of melting
• At the surface it is 0°C
• Further down is lower due to pressure

Temperature (Warm Based) Glaciers

• Water at the surface in summer- may end up at base via fluvio-glacial system.

Polar (Cold Based) Glaciers

• Temperatures at surface too cold for water to exist at any point of the year

Warm Based Glaciers

• High altitude locations
• Steep Relief
• Basal Temperature at or above PMP
•            Water at base of glacier between ice and ground
•            Rapid movement rates
•            20 to 200m per year
• Significant amount of glacial erosion
• Maximum impact on landscape

Cold Based Glaciers

• High latitude locations
• Low Relief
• Basal temperatures below PMP
• Ice frozen to bedrock
• Very slow movement rates
• Few metres per year or less
• Limited movement or erosion
• Limited landscape impact

• Gravity leads to glacial ice movements
• Gradient- Steeper Gradient = faster movement
• Thickness of ice affects basal temperatures and PMPs
• Internal Temperatures of the ice- variations can allow movement of one area of ice relative to another
• Glacial Budget- positive budget causes glacial advance
• Nature and location of ice in the glacier can also affect movement