University of Alaska Fairbanks    |    Scenarios Network for Alaska + Arctic Planning


Physiography is the large-scale topography of an area. Alaska is divided into four major divisions from south to north: the Pacific Mountain System, the Intermontane Plateaus, the Rocky Mountain System, and the Interior Plains (Arctic Coastal Plain).

The Pacific Mountain System consists of two arcs. The more northerly includes the Coast Mountains between southeastern Alaska and Canada, the Alaska Range, the Aleutian Range, and the Aleutian Islands. The southern arc consists of the island range of southeastern Alaska, the Fairweather Range, the St. Elias Mountains, the Kenai-Chugach Mountains and Kodiak Island. Between the two arcs is a trough composed of the Inland Passage, the Copper River Lowlands, the Cook Inlet–Susitna Lowlands and Shelikof Strait. This trough is broken by the Wrangell and Talkeetna Mountains.

The Intermontane Plateaus lie north and west of the ·Alaska Range. They consist of dissected uplands, broad valleys, and lowland basins floored with alluvial deposits. The great river systems of the Yukon, Koyukuk, Porcupine, Tanana, and Kuskokwim Rivers flow through this area.

The Brooks Range rises to over 9,000 feet in the east but is lower to the west. Glaciation during the Pleistocene carved this rugged landform, which persists with little change. The arctic foothills to the north consist of rolling plateaus and low mountains.

The Arctic Coastal Plain, an extension of the Great Plains consists of a broad level plain underlain with permafrost and pockmarked by thousands of shallow lakes and swamps.