7.1 Glaciers

Ice Age

• A period of time when much of Earth’s land is covered by glaciers.

Glacier

• A thick mass of ice originating on land from the compaction and recrystallization of snow that shows evidence of past or present flow

Snowline

• Lowest elevation in a particular area that remains covered in snow all year.

Valley Glacier

• A glacier confined to a mountain valley, which in most instances had previously been a stream valley.

Ice sheet

• Enormous ice masses that flow in all directions from one or more centers and cover everything but the highest land.

Till

• Sediment of different sizes deposited directly by a glacier

Moraine

• A ridge of unsorted sediment left by a glacier

Glacial trough

• V-shaped or U-shaped valley cut by glacial movement.

Key Concept

• A valley glacier is a stream of ice that flows between steep rock walls from a place near the top of the mountain valley

Key Concept

• Ice sheets are sometimes called continental ice sheets because they cover large regions where the climate is extremely cold. They are huge compared to valley glaciers.

Key Concept

• The movement of glaciers is referred to as flow. Glacial flow happens two ways : plastic flow and basal slip.

Key Concept

• The glacial budget is the balance or lack of balance between accumulation at the upper end of a glacier and loss, or wastage, at the lower end.

Key Concept

• Many landscapes were changed by the widespread glaciers of the recent ice age.

Key Concept

• Glaciers are responsible for a variety of erosional landscape features, such as glacial troughs, hanging valleys, cirques, arêtes, and horns.

Key Concept

• Glacial drift applies to all sediments of glacial origin, no matter how, where, or in what form they were deposited. There are two types of glacial drift: till and stratified drift.

Key Concept

• Glaciers are responsible for a variety of depositional features, including moraines, outwash plains, kettles, drumlins, and eskers.