How does a glaciated landscape affect surface drainage ?
Continental glaciers deposit thick blankets of till, an unsorted jumble of material ranging from clay to boulders, as the ice front retreats at the end of an ice age dropping in place the rubble frozen in the ice. Thick till fills in the low places making the landscape relatively flat. Buried beneath the till lie the former stream and river valleys that collected and carried away the runoff 4 from the pre-glacial landscape. The slow process of geologic erosion make take tens or hundreds of thousands of years to cut a new network of streams into the fabric of the till plane, gradually restoring the ancient watersheds 1 obliterated by the ice sheet.
