Glacial Processes
- Glaciers alter the landscape through a number of processes such as:
- Erosion
- Entrainment
- Transportation
- Deposition
- Erosion is the combination of:
- Abrasion (sand paper action) where individual stones lead to stations and chatter marks and are ground into rock flour
- Plucking or glacial quarrying is a two stage process of initial widening of rock fracture joints and encapsulating and then the removal of loose material in the ice
- Fracture and traction results from the sheer weight of the moving ice as it passes over the bedrock, which leads to basal pressure melting and freezing
- Dilation happens as overlying material is removed, which releases pressure and causes fracturs in the rock
- Meltwater erosion is very similar to river erosion, except the meltwater is under hydrostatic pressure. The erosion can be mechanical or chemical as glacial meltwater can dissolve minerals, particularly limestone
- Entrainment is the capturing of material into the glacial ice and can be:
- Supraglacial - where material falls onto the surface of the glacier
- Subglacial - where material is transported from the base and sides of the glacier
- Englacial - sediments transported within the glacier
- Transportation is mostly basal, but in valley glaciers, material is transported englacially and supraglacially
- Glacial material is carried both horizontally and vertically by the movement of ice itself, but meltwater will also carry material through the complex glacial drainage systems, and by glacial deformation
- Deposition occurs at the margins and base of the glacier
- It can occur directly as till
- Or released with meltwater as fluvio-glacial debris