Ch. 22 Glaciers

Glacier

A large mass of ice formed on land that moves under its own weight.

Percentage of Earth's freshwater in glaciers

About 77%.

Cryosphere

The part of the hydrosphere that is frozen (ice, snow, glaciers, permafrost).

Effects of glaciers on global climate

Their whiteness reflects sunlight, cooling Earth, and their ice stores large amounts of water that can raise or lower sea levels.

Continents with glaciers

Every continent except Australia.

Types of glaciers

Alpine (valley) and Continental (ice sheet) glaciers.

Alpine glacier

Long, narrow, and confined to mountain valleys or old stream channels.

Continental glacier

Vast, continuous mass of ice that covers large land areas like Greenland and Antarctica.

Glacier formation

From accumulated snow that compresses into ice under pressure and begins to flow downslope.

Glacier movement

By internal flow (plastic deformation) and basal sliding (sliding over the bedrock).

Plucking

When moving ice lifts and removes blocks of rock from the bedrock.

Glacial abrasion

Grinding and scraping of bedrock by rock fragments embedded in the ice.

Striations

Scratches or grooves on bedrock left by rocks dragged by moving ice.

Antarctic ice sheet size

About 13 million km², up to 4000 m thick, containing ~65% of Earth's freshwater.

Nunataks

Mountain peaks that protrude above the surface of an ice sheet.

Greenland ice sheet size

About 1.7 million km² (1/8 the size of Antarctica) and holds ~11% of Earth's freshwater.

Iceberg

A large mass of ice that breaks off (calves) from a glacier or ice shelf and floats in the ocean.

Iceberg visibility

About one-sixth.

Sea ice

Ice formed by the direct freezing of ocean water.

Pack ice

Sea ice that covers the ocean surface and can be broken into patches (ice floes) by wind and currents.

Leads

Narrow strips of open water between ice floes.

Erratics

Large boulders transported and deposited far from their source by glaciers.

Moraine

A ridge of glacial debris (till) deposited by a glacier.

Terminal moraine

Marks glacier's furthest advance.

Recessional moraine

Marks temporary halts during glacier retreat.

Drumlin

A smooth, elongated hill formed by glacial till, aligned with ice movement.

Esker

A winding ridge of sand and gravel formed by streams running beneath a glacier.

Outwash plain

A broad, flat area of sediment deposited by meltwater beyond a glacier.

Pluvial lakes

Lakes formed during periods of increased rainfall due to glacial climate conditions.

Lake Bonneville

A large ancient lake that shrank to form the Great Salt Lake and Bonneville Salt Flats.

Great Lakes formation

Carved out by glaciers that created shallow basins.

Cirque

A bowl-shaped basin where snow and ice accumulate at a glacier's head.

Crevasses

Deep cracks on the upper brittle surface of a glacier.

Tarn

A small mountain lake formed in a cirque after a glacier melts.

Fjord

A glacial valley flooded by the sea.

Lateral moraine

Ridge of debris deposited along the sides of a glacier.

Medial moraine

Ridge of debris formed when two glaciers merge and their lateral moraines join in the middle.

Terminal moraine (alpine)

Ridge of debris marking the farthest extent of a glacier's advance.