(6) depositional landforms

• what is the glacier sole


  the lower few metres off a glacier that contain debris picked up from the bed
• what is the glacier bed


  bedrock, or debris, over which the glacier flows
• what is subglacial debris


  debris which has been released from ice at the base of a glacier
• what is moraine

  landforms associated with the deposition of till from within or below a glacier, so poorly sorted and angular. they are lines or a series of mounds of material mainly running across glacial valleys
• what are the 3 main types of moraine

  • terminal
  • lateral
  • recessional
• what is terminal moraine


  a prominent ridge of glacial debris formed when a glacier reached its maximum limit during a sustained advance
• what is lateral moriane


  a ridge of material running along the edge of a glacial valley from material that has accumulated on top of a glacier. as the glacier retreats, this material sinks through the ice to the ground and is deposited
• what is recessional moraine


  a series of ridges of debris running transversely across glacial troughs, broadly parallel to each other and to the terminal moraine. form during a temporary stationary phase in otherwise general retreat.
• what are erratics


  an individual piece of rock, varying in size from a small pebble to a large boulder with a different geology to the area in which they have been deposited in.

  likely to have been plucked or added to the supra glacial in one geology and then transported and deposited in an area with a different rock type
• what is a drumlin


  a streamlined hillock, commonly elongated parallel to the former ice flow direction, composed of glacial debris, and sometimes having a bedrock core, formed beneath an actively flowing glacier
• what are the two theories of drumlin formation


  • sub-glacial deformation
  • sub-glacial flooding
• subglacial deformation model of drumlin formation


  as the glacier meets the moraine, it begins to travel over it. it does not move with it because it does not have enough energy, but it also cannot erode the resistant rock in the moraine. as it moves over the moraine, it begins to smooth the material down the back slope.
• subglacial flooding model of drumlin formation


  Turbulent water during the floodstage erodes giant drumlin-shaped scours in the base of the ice, which are then infilled with sediment as the flood wanes and as the ice presses down onto its bed.

  This is the cavity-fill drumlin and explains how fluvially-derived sediments may appear in drumlins.
• how are till sheets formed


  formed when a large mass of unstratified drift is deposited at the end of a period of ice sheet advance
• what is till


  unsorted mixture of rocks, clay and sand that was mainly transported as supra glacial and en glacial debris and deposited when the ice melted
• what are the two types of glacial till

  • lodgement till
  • ablation till
• what is lodgement till


  subglacial material that was deposited by the actively moving glacier.
• what is ablation till

  produced at the snout where the ice melts.