36. Glacial Degradation and Aggradation

Photo 63: Athabasca Glacier, Alberta. 2011-05-18

Cryosphere

In the previous posts I have talked about the hydrosphere and the oceans, about the lithosphere and how rocks and rivers work, about the atmosphere and weather, little bits about the biosphere, and now it is time for the cyrosphere, the sphere of frozen water.

Athabasca Glacier

Photo 63 is the well-known Athabasca Glacier, feeding the Mackenzie river-basin, which eventually flows into the Arctic Ocean. A glacier is a body of ice, formed on land, and is always in motion. Mountain glaciers, like those in the Rockies and Alps, are located in valleys with sometimes steep slopes. Contrary, continental glaciers are not confined by a valley: for example the ice cap of Antarctica and Greenland.

Glacial Processes

Glaciers consist of compacted snow. As snow falls, it is compacted due to gravity and slightly melts in summers, thus creating a hard layer of ice. A glacier is an open system, which means it is not self-regulating but it is influenced by forces from outside. Glaciers are fed by new layers of snow in the zone of accumulation, which is usually the top of a glacier. Glaciers loose ice at the bottom, which is the zone of ablation.

Cirque

Some glaciers form in a cirque (or corrie), as show in photo 64. A cirque is a relatively flat shelf on a steep slope. Some cirques have a small lake in them and others permanent glaciers. Cirques often form, like in photo 64, because ice and snow converge from three directions. This creates erosional forces that often enlarge a cirque.

Photo 64: A cirque glacier in Jasper National Park. 2011-05-18