Glaciers

Nebesna glacier with Mt Blackburn
Nabesna glacier with Mt Blackburn in the background, Wrangell-St Elias National Park and Preserve.

NPS/Bev Goad

Approximately one quarter (4.6 million acres) of Alaska's glaciers exist within national parks. Glaciers require three conditions to form: abundant snowfall, cool summers, and the gravitational flow of ice. Glaciers form in land areas where annual snowfall is greater than annual snowmelt. Some areas in Alaska, such as the Harding Icefield in Kenai Fjords National Park, receives an average of 60 feet of snow each year. Large amounts of snowfall, combined with cool summers and gravity, form multiple, connected glaciers over time, known as an icefield.

Glaciers tell stories of the Earth's history; they shape the Earth's surface as they move and form valleys and mountains. Glacial ice documents weather and life from many years past. Tidewater glaciers are those that terminate in the sea. The ice that calves off these glaciers provide important habitat to ice-dependent species, such as seals.

Glacier Monitoring Story Map

Above is an interactive story map with videos, images, maps and narrative that describe changes in Alaska's glaciers.


Glacier Terminology

Ablation

the retreat and degradation of glaciers

Advance

glacier flow exceeds ablation and the terminus extends beyond its previous point

Calve

process of ice breaking off at a glacier's terminus

Crevasse

a large crack in the surface of a glacier produced by the stress of glacial flow

Hanging

a glacier that clings to the side of a steep mountain or one that terminates at a cliff

Moraine

a deposit of rock debris shaped by glacial flow and erosion

Tidewater Glacier

a glacier that terminates in the sea and discharges icebergs and other small pieces of ice

Terminus

the lower end, or snout, of a glacier