Advances are characterized by a convex-shaped terminue. Collectively, these deposits are called glacial drift. Till refers to the debris deposited directly by the glacier. Retreat results when the glacier is ablating at a faster rate than its movement downvalley. Also called Till.
Glaciers exist where, over a period of years, snow remains after summer's end.
The flow of ice down a steep gradient often results in crevasses. The wave of ice may move at 2-6 times the velocity of surrounding thinner ice. Piles of loose unsorted rocks along the side margins of the glacier. The rocks may be pushed thereby moving ice or dumped from the glacier's rounded surface. They appear as dark streaks of rock along the glacier center line.