Glacial erosion entrains a boulder of the bedrock. ... As the glacier retreats, the boulder is deposited on a different type of bedrock, forming a glacial erratic. Erratics can range from large boulders to smaller stones and pebbles. All erratics are of a different rock type.

What are formed by glacial deposition?

U-shaped valleys, hanging valleys, cirques, horns, and aretes are features sculpted by ice. The eroded material is later deposited as large glacial erratics, in moraines, stratified drift, outwash plains, and drumlins. Varves are a very useful yearly deposit that forms in glacial lakes.

What are erratics in glaciers?

Glaciers can pick up chunks of rocks and transport them over long distances. ... When they drop these rocks, they are often far from their origin—the outcrop or bedrock from which they were plucked. These rocks are known as glacial erratics. Erratics record the story of a glacier's travels.