Glaciation and Glacial Erosion

Introduction At any place on the land where more snow accumulates than is melted during the course of a year, the snow will gradually grow thicker. As the snow piles up, the increasing weight of snow overlying the basal layers causes them to recrystallize, forming a solid mass of ice. When the accumulating snow and ice become so thick that the pull of gravity causes the frozen massto move, a glacier is born.

A glacier is a permanent body of ice, consisting largely of recrystallized snow, that shows evidence of downslope or outward movement due to the pull of gravity. Glaciers are found in regions where average temperature is so low that water can exist throughout the year in a frozen state. Most glaciers are found in high altitudes or at high latitudes.

Athabasca Glacier (Alberta)

Crowfoot Glacier (Alberta)

Glacial Erosion Three major erosional processes occur at the base of a glacier. The first occurs when the loose rock and sediment become incorporated into the moving ice. This sediment leads to scouring caused by the abrasive action of rock and sediment in the ice

Plucking Plucking is the process of particle detachment by moving glacial ice. In this process, basal ice freezes in rock surface cracks. As the main body of the glacial ice moves material around the ice in the cracks is pulled and plucked out.

Freeze-Thaw  Freeze-thaw is when melt water or rain gets into cracks in the bed rock, usually the back wall. At night the water freezes, expands and causes the crack to get larger. Eventually the rock will break away.

Alpine Glaciation

Glacial Deposition A large part of the surface of a glacier is covered with a coating of sediment and rock debris. Much of the debris that is added to the ice of the glacier is eventually delivered to the snout because of the continual forward flow of glacial ice. This material can be deposited as till or a moraine

Glacier snout and outwash plain

Eskers

Kettle Lakes

Drumlins