Fluvioglacial landforms

• Fluvioglacial landscape


  Divided into 2 categories: Ice contact and Proglacial meltwater
• Categories of Fluvioglacial Landforms

  • Ice Contact
  • Kames and kame terraces
  • Eskers
  • Proglacial
  • Sandurs/outwash plains and varves
  • Pro-glacial lakes
  • Meltwater channels
  • Kettle holes
• Meltwater channels


  Formed from erosion due to the flow of meltwater beneath or close to an ice-sheet margin
• Meltwater channels


  • Typically steep sided, deep and straight
  • Have a high discharge rate and a turbulent flow
  • The larger the meltwater channels, the more significant the levels of meltwater erosion and size of deposition
• Types of meltwater channels

  • Subglacial
  • Englacial
  • Lateral
  • Surface
  • Proglacial
• Subglacial meltwater channels


  Found beneath the glacier, with an undulating long profile, and complex, braided stream systems
• Englacial meltwater channels


  Where meltwater streams form within the body of the glacial ice - they do not have to exit
• Lateral meltwater channels


  Meltwater streams that follow the glacial edge, either within the glacier or on its surface
• Surface meltwater channels


  Meltwater flows over the surface of the glacier; the meltwater may flow into crevasses, moulins or supraglacial lakes
• Proglacial meltwater channels


  Where meltwater drains from the front of the glacier, downslope and away from the ice margin, eventually forming a network of shallow, sedimented braided channels that are separated by gravel bars (eyots)
• Meltwater channels have the same processes as rivers: hydraulic action, abrasion, corrosion, attrition
• Meltwater erosion


  More erosive due to the downward pressure of the ice 'squeezing' the meltwater, causing it to flow faster; plus the meltwater carries more debris, which aids in the abrasion and attrition processes
• Meltwater channels


  Deep, wide troughs that carry vast amounts of fast-flowing water and are, therefore, highly erosive
• As the glacier retreats


  The deep meltwater channels are left with shallow, slow-flowing streams of water
• Outwash plains and varves

  As meltwater begins to descend, the velocity of the water begins to slow, allowing for the formation of a network of shallow, sedimented split channels, that are separated by gravel bars that eventually make up the outwash plain or sandur
• Traction, saltation, suspension and solution processes

  Transport the eroded material within the meltwater channels
• Varves


  Layers of sorted sediment deposited on the valley floor as the decreasing velocity reduces the ability of the meltwater to 'hold' the debris
• Varves are frequently defined as a type of glacial lake sediment because they are common in glacial lakes, but they occur in different environments where sediment layers are laid down annually and not just in glacial lakes
• Kettle holes


  Hollows formed when blocks of ice calved from the main glacier and left on the outwash plain as the glacier retreated, the ice block subsequently melts, leaving a depression in the sediment deposits (varves) of the outwash plain
• Kettle lakes


  Water-filled kettle holes
• Eskers


  Long, winding ridges of sand and gravel, running parallel to the glacier, deposited by subglacial meltwater streams and can stretch for several kilometres and reach heights of 30m
• As the glacier retreats

  The subglacial meltwater stream dries up, and the load remains as an esker
• Eskers show the position of past glacial tunnels
• Kames


  Mounds of sand and gravel found on the glacial valley floor, formed as supraglacial meltwater streams collect in surface depressions and deposit layers of debris, which is then dumped onto the glacial valley floor as the glacier retreats
• Kame terraces


  Piles of deposited debris, left by meltwater channels, running between the glacier and the valley sides, similar in appearance to the lateral moraines, but kames are sorted layers (stratified) with the heaviest gravel at the base and finer sediments on top
• Proglacial lakes


  Can form in front of glaciers, particularly when the terminal moraine acts as a dam for the meltwater, as the proglacial lake develops, velocity is lost and sediment is deposited - these deposits are known as deltas
• Delta kames


  Formed as glacial retreat dumps the deltas on the glacial valley floor
• Crevasse kames


  Small hummocks of left behind, glacial surface deposited sediments