Glacier Landform System (Edexcel A Level Geography)

• 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

• Glacial landforms develop at different levels:
  • Micro 
  • Meso
  • Macro
• Micro-scale features
  • These are small-scale landforms up to 1m in length
  • Examples include striations
  • Grooves
  • Chatter marks 
• Meso-scale features
  • Medium-scaled features such as:
    • Drumlins
    • Ribbon lakes
    • Roche moutonnées
• Macro-scaled features
  • Large landforms such as:
    • Pyramidal peaks
    • Glacial troughs
    • Cirques/tarns/corries

Process morphology

• Different parts of the glacier are linked to different geomorphic processes
• This is where different processes create differently shaped landforms at different scales, times and places
• General glacial process morphology includes:
• Sub-glacial
  • Beneath the ice, the immense pressure and weight subject the bedrock to grinding, scratching, and polishing
  • Warm-based glaciers will undergo fluvial processes due to glacial meltwater
• Glacial margins
  • Both glacial and fluvio-glacial processes occur at the sides and front of the glacier
• Proglacial
  • Fluvio-glacial processes dominate landscape features at the front of glaciers, caps, and ice sheets
• Paraglacial
  • Surface adjusts to glacial retreat through mass movement, and rapid erosion until dynamic equilibrium is achieved
• Periglacial
  • Permafrost features respond to freeze-thaw rather than ice movement 
  • Rapid melting can lead to transitional paraglacial features, as a new equilibrium is reached

• Collectively, glacial landforms create a distinctive glacial landscape
• They can be separated into upland and lowland features
• Identifying how and where these features originate, can help in understanding the extent of past ice cover 
• Known as inversion modelling, it involves mapping areas of past glaciation combined with analysis of current deposits to identify relict glacial landscapes and features and includes:
  • Hutton's principle of uniformity, where looking at present day environments, is key to understanding past processes and their role in forming the landscape, for example:
  • Pingos in northern Canada helped identify collapsed craters on the North York Moors as relict pingos from the last ice age
• Upland landscape 
  • High altitudes of hills and mountains
  • Examples include:
    • Arete
    • Corrie
    • Pyramidal peak
• Lowland landscape
  • Low altitude such as valley floors and coastal plains
  • Examples include:
    • Drumlins
    • Pingos
    • Patterned ground
• Landscapes further identify into relict and active environments
  • Relict landscapes are no longer influenced by ice masses but do feature localised features from past glaciation
  • Active landscapes are being acted upon by ice masses and experience the full glacial development