glacial depositional landforms

• Most of northern Britain is covered by till, composition depends on rock types that the glacier moves across.   
• Glaciers left behind superficial unlithified deposits of till and boulder clay with outwash sands and gravels at the edges. 

  • Mapping edges of different layers of till can show size of ice sheet and number of glacial periods
• Till is unable to be dated, other than saying if its older or younger than the till on top. Rely on interglacial deposits with organic matter for dating. 

  • A newer glacier may also remove till from an earlier one. 
• Moraine is a mass of rock fragments carried down and deposited by a glacier. 
• Lateral moraine falls onto the sides of a glacier due to freeze-thaw weathering oof valley sides. 
• Medial moraine in centre of glacier where two glaciers meet and their lateral moraines join. 
• Terminal moraine is at the end of the glacier. 

  • Maximum advance of glacier 
  • Builds up at end of glacier when glacier finishes at one place for a long period of time 
  • Often curved as a centre of glacier faster moving so further forward 
  • Slope of 30 - 25 degrees as any steeper, slope is unstable 
• Recessional moraine:

  • Glacier retreats as melting greater than ice supply 
  • If pace of retreat slows then new moraine deposited 
• A terminal or recessional moraines can hold meltwater ribbon lakes. 
• Erratic's:

  • Rock fragment of different lithology to underlying rock type 
• Drumlins:

  • Deposited underneath slow moving thick ice sheet 
  • As slow moving there is deposition rather than erosion 
  • Ice movement creates streamlined shape 
  • Found in a swarm 
  • Cannot see them forming, but can be observed today 
• Esker:

  • Meltwater channels form under glacier during summer 
  • Subangular, moderate sorting and medium grained 
  • Cross bedding and imbricate structures 
  • Sediments then deposited in winter when water supply reduces of if a new tunnel is created 
  • Wavy deposit created appears to meander