Glacial depositional landforms

Glacial depositional landforms

1. Drumlins

   • Smooth, oval shaped hills found in lowland locations on valley floors where the ice has emerged from the highlands
   • Can be as long as 1.5km (most smaller) and up to 60m in height
     • Poorly sorted glacial till
   • Steep end (stoss) and gently sloping end (leeside)
     • Elongated in direction of ice advance
       • Often found in-groups known as swarms 'basket of eggs topography'
   • Eden Valley, Cumbria
   • Debate over exact formation of drumlins as formed sub glacially and only revealed once ice has disappeared
     • Lodgement of subglacial debris as melts out of basal ice
     • Reshaping of previously deposited material during subsequent re-advance
     • Accumulation of material around a bedrock obstruction (rock-cored drumlins)
     • Thinning of ice as spreads over lowland area reducing ability to carry debris, continued forward movement streamlines feature

2. Erratics

   • Individual pieces of rock with distinctive geology different from the area in which they were found
     • May vary in size from small pebbles to large boulders
   • Norber Erratics - Yorkshire Dales
   • Pieces of rock which have been transported by a glacier from one area and deposited in an area of different rock type
     • Likely they were eroded by plucking and entrained in the glacier or were frost-shattered from the valley sides, becoming supra-glacial debris by rockfall