Steep cliffs that occur between tributary valleys as a result of movement of ice down the valley. A thin sedimentary layer or pair of contrasting layers that represent the depositional record of a single year. The underlying portion of a glacier where movement occurs without fracture occurring. The upper brittle portion of the glacier that is characterized by chaotic fracturing and the development of deep crevasses. Alpine glaciers do not occur in the tropics.
Ice sheets spread outward under their own weight.
The North Pole is covered by a continental ice sheet. When a glacier retreats, the ice flows back uphill. Ice by itself is very abrasive to rocks. Drumlins are steeper on the upstream side. Glacial streams are usually braided because of their heavy sediment load.