M127 Aleutian Oceanic Meadow--Heath Province

Aleutian Islands, Alaska Peninsula, West Kodiak Island 22,200 mi2 (57,500 km2)

Land-surface form.--The islands that chiefly make up this province are mountainous, rising steeply from the sea. They contain more than 75 volcanoes, about half of which are know to have erupted during the last 200 years. Altitudes of the volcanoes decrease southwestward from 7,500 ft (2,300 m) at Mount Katmai on the Alaska Peninsula to 6,000 ft (1,800 m) on the Aleutian Islands. Not much of the land on the islands or on the peninsula is level. Steep slopes prevail all the way to water's edge, and shores are rocky and craggy. The Alaska Peninsula has intensely glaciated mountains indented with fjords that are bordered by cliffs. Several large lakes are on the peninsula.

Treeless slopes along the Pacific coast of the Alaska Peninsula, Aniakchak National Monument. Treeless slopes along the Pacific coast of the Alaska Peninsula, Aniakchak National Monument. (Photo: National Park Service.)

Climate.--The climate is similar to that on the arctic coastal plain, except it is a marine phase (described above for the Bering Tundra [Southern] Province). Winters are less severe than those on the coastal plain, with temperature ranges of 18 to 27F (10 to 15C), as compared to a 54F (30C) range on the coastal plain. The climate is characterized by fog and rain, with the amount of precipitation varying little from month to month. Annual precipitation varies from 21 in (530 mm) to more than 78 in (2,000 mm). In general, smaller islands receive less precipitation than larger islands. Winds are often severe on the islands. Pacific Ocean water moving northward through the straits between the islands produces complex mixing with Bering Sea water, including upwelling. The Pribilof Islands in the Bering Sea are about at the southern limit of the arctic ice pack in winter.

Vegetation.--Trees are absent from the Aleutian Province, although there are a few shrubs, chiefly dwarf willows. At lower elevations, there is a luxuriant growth of tall grasses, flowering plants, and ferns, with thickets of low willows in some places. A little higher up, several types of heath cover vast areas. The boreal forest and coastal rainforest are slowly encroaching from the east on the area of this province. This is explained by the assumption that the distribution of the vegetation is not yet adjusted to the climatic conditions produced by retreat of the last continental glaciers.

Soils.--About 30 percent of the area consists of high mountains without soil cover. Dominant soils are Inceptisols formed from volcanic ash or pumice, with large components of pyroclastic materials. Permafrost is generally absent.

Fauna.--The Aleutian Islands support no land mammals larger than foxes. Marine mammals such as seals, sea lions, and sea otters are abundant, using the islands for hauling out and as rookeries.

Bald eagles and hawks are prevalant predators, feeding on the millions of sea birds that use the islands and rocks as rookeries.