Glacial Movement
Geography: Edexcel A Level, topic 2.3.2
Factors Affecting Movement
Glaciers move by a range of different processes and at different rates. A range of factors influence rates of glacial movement.
Altitude
- The potential energy gained from height can increase glacier movement.
- But, high-altitude glaciers are more likely to be cold-based for longer time periods in a year so won't move as much.
Slope and lithology
- Steeper sloped valley glaciers have higher rates of flow.
- Lithology influences bed topography. Easily eroded rocks (e.g. sandstone) are more likely to eroded, creating deformations which may slow movement down.
Mass balance
- Areas of accumulation have slower rates of movement than areas of ablation.
Types of Glacial Movement
Glaciers move by a range of different processes and at different rates.
Basal slip
- Basal slip is linked to the pressure melting of ice that takes place along its base.
- Ice normally forms from water at a temperature of 0oC, but the temperature at which water freezes is reduced under pressure.
- As a glacier moves it will exert pressure and so some melting may take place at its base.
- A thin film of water then exists between the glacier and the bedrock.
- This film reduces friction, acts as a lubricant, and allows the glacier to slide.
Regelation creep
- Regelation is the re-freezing of water under a glacier when pressure reduces after meeting an obstruction.
- Pressure melting takes place on the upstream side, creating a film of water, and regelation takes place on the downstream side.
- The combination of both processes allows a temperate glacier to slide downhill.
Internal deformation
- Internal deformation is small in scale and takes place in all glaciers, but it is the most common form of movement in cold-based glaciers.
- It takes place where the ice crystals set themselves in line with the movement of the glacier and slide past each other.
- Movement can occur along lines of weakness called cleavage planes . This is sometimes called laminar flow.
Test yourself on Glacial Movement
Which of the following areas has the slowest rate of movement?
Which of these statements are true?
What allows the glacier to slide in basal slip?
Which of the following are types of glacial movement?