till

 

 

Till sheet or plain

Definition: a uniform blanket of glacial deposits in a lowland

Till sheets may cover low-lying districts towards the margins of former ice sheets. The  bedrock surface may be highly eroded but it is concealed beneath a thick cover of glacial till, sands, and gravel. The compact, mud-rich till gives a poorly drained surface with numerous bogs, lakes, and slow-moving, wandering streams. Large till plains occur south of the Great Lakes in North America in regions at the margins of the last and earlier Laurentide ice sheets.