Glacier Landform System (Edexcel A Level Geography)

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

Glacial Landforms

• 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

Upland & Lowland Landscapes

• 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