Glaciated Landscapes

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  • Glaciated Landscapes
    • The components of open systems
      • Inputs
        • Kinetic, thermal and potential energy
        • Material from glacial deposition
        • Weathering
        • Mass movement
      • Outputs
        • Melting
        • Evaporation
        • Sublimation
      • Throughputs
        • Sediment in the glacier
        • Basal sliding
      • System feedback
        • When the outputs and inputs are the same a state of equilibrium exists
          • The glacier stays the same
        • When the equilibrium is upset the glacier can grow or melt
        • If the equilibrium is upset the system changes to restore it - this is called dynamic equilibrium
    • Glacier mass balance
      • This is the difference between the accumulation and the ablation
      • At the top of the glacier you get the accumulation zone
      • There will be seasonal changes
    • Physical features that affect glaciated landscapes
      • Climate
        • Wind can erode and transport and deposit material
          • These aeolian processes help to shape the landscape
        • Precipitation
          • This provides the inputs of snow rain and sleet to the glacier
          • This determines the mass balance of the glacier
        • Temperature
          • If temperatures rise above 0 degrees the ice will start to melt
      • Geology
        • Lithology
          • This is the physical and chemical composition of the rocks
          • Rock with a weak lithology has little resistance to erosion
        • Structure
          • This is the properties of the rock e.g. jointing, fracturing
          • This can affect the permeability of the rock
      • Latitude and altitude
        • High altitude locations are colder
        • Locations on high latitudes are colder
          • Glaciers here generally form under the influence of stable ice sheets
      • Relief and aspect
        • The steeper the relief of the landscape, the greater the potential energy so the qlacier will move downhill faster
        • If a slope faces away from the sun, the temperature will stay cooler for longer
    • Different types of Glacier
      • Ice sheets
        • These are large areas of ice -  there are only 2 - Greenland and Antartica
      • Valley glacier
        • These are confined by valley sides - they follow the course of river valleys
      • Warm based
        • Usually have:
          • High altitude locations
          • Steep relief
          • Rapid rates of movement
        • The base of the glacier is usually above melting point
        • e.g. Andes, Rockies
        • These are very dynamic
      • Cold based
        • Usually have:
          • High latitude
          • Low relief
          • Very slow rate of movement
          • Basal temperatures lower that the melting point
        • These are not very dynamic
    • Glacier ice
      • Glacier ice is formed when the snowflakes are compressed and the air is squeezed out - leaving highly dense ice
    • Movement
      • Factors that influence movement
        • Gravity
        • Gradient
        • Thickness of ice
        • Internal temperature of the ice
        • Glacial budget
      • The sides and the base of the glacier move move more slowly than the middle and the top because of friction
      • Basal sliding
        • Warm based glaciers
        • Slippage - where the ice flows over the valley floor using melt water as a lubricant
        • Creep/ relegation - when ice deforms under pressure due to obstacles of the valley floor
          • The ice just moulds around the object
        • Bed deformation - the ice is carried by saturated bed sediments moving beneath it on gentle gradients
      • Internal deformation
        • Cold based glaciers where the basal temperature is below zero
        • Intergranular flow - when individual ice crystals re-orientate and move in relation to each othe
        • Laminar flow - when there is movement of individual layers in a glacier
    • How glaciated landforms develop
      • Weathering
        • Chemical
          • Oxidisation
            • Some rocks react with the oxygen in the air
          • Carbonation
            • Rainwater in weak carbonic acid - it reacts with limestone
          • Solution
            • Some rocks dissolve in water
          • Hydration
            • Water is added to minerals to create minerals with a larger volume
        • Physical
          • Freeze-thaw
          • Pressure release
            • When overlying rocks are removed by erosion and weathering, or when ice melts, the underlying rock expands and fractures parallel to the surface
          • Frost shattering/ onion skin
            • Water trapped in rock pores freezes and disintegrates the rock into small pieces
        • Biological
          • Tree roots
          • Acids from algae
      • Mass movement
        • Rock falls
        • Slides
          • Rotational slides (slumps) - take place along a curved slip plane
      • Glacial processes
        • Erosion
          • Plucking
            • Water seeps into cracks along the bottom and sides of the valley - this then freezes and the rock becomes attached to the glacier - pulling it away
          • Abrasion
            • This is affected by many factors e.g. size of rock particles, thickness of the ice, the hardness of the rock
        • Nivation
        • Transportation
          • Rock falls
          • Avalanches can move large rocks
          • Debris flows - melting ice can mix with scree, soil and mud
          • Aeolian deposits -  material moved by the wind
          • Plucking
          • Abrasion
          • Englacial debris is within the glacier
          • Subglacial debris is embedded in the base of the glacier
        • Deposition
          • Till
            • Lodgement till
              • This is deposited as the glacier advances being pushed into the existing valley floor
            • Ablation till
              • Left when the glacier retreats
            • Usually: angular, unsorted, unstratified

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