Glaciers

From Great Lakes Wiki

Glacier Terms

Accumulation area: The ice accumulation zone at a high elevation.

Ablation area: The ice loss zone, located below the accumulation area.

Terminus: The face of the glacier

Zone of plastic flow: Bottom layer of glacier experiencing the most intense pressure, conforms to floor upon which it travels.

Zone of brittle flow: Upper layers, approximately 150 feet, which rigidly carve out its surroundings.

Crevass: The shoot in which the glacier simultaneously moves through and reshapes.

Glacier Behavior

Glacier A's advancing face is created when more ice amasses than melts. In glacier B the melt surpases the amount of accumulation and 'retreats.' Even though it appears the glacier moves backwards over time, all of its melt continually flows the same downward direction.

Glacier C advances over hundreds of years before its terminus begins retreating. A large unique crevass is formed, water winding down it from the glacier. Over more centuries the glacier proceeds another advance, its zone of plastic flow gliding along the bottom already carved. The zone of brittle flow gives the pre-existing valley a new look, pushing and dragging rocks, widening the gap until conditions change and glacier C retreats. The Great Lakes, among many other spectacular land formations, were formed by glaciers.

Sources

Wrangell-St. Elias National Park & Reserve