Region extending 1,000 km/600 mi across northern Alaska, from Point Hope in the west to the border with the Yukon Territory. The term is either used specifically to describe the high plateau (altitude 760 m/2,500 ft) in the foothills north of the Brooks Range, or of the entire division extending north for 400 km/250 mi from the Brooks Range to the Arctic Ocean. The principal river crossing the region is the Colville.
Geologically, the North Slope is a northern extension of the Great Plains. The North Slope Borough (area 235,575 sq km/90,955 sq mi, population 6,000) is predominantly a region of tundra with little vertical relief. In places this is underlain by a layer of permafrost up to 300 m/1,000 ft thick, which prevents drainage and gives rise to many ponds and shallow lakes. Winds are strong and rainfall is light here. The chief population centre is Barrow; other communities are Point Hope, Point Lay, Wainwright, Atqasuk, Nuiqsut, Anaktuvuk Pass, and Kaktovik. A National Petroleum Reserve covering some 96,000 sq km/37,000 sq mi in the centre and west of the region was established in 1923. Although the discovery of huge petroleum and natural-gas reserves in Prudhoe Bay in the northeast in 1968 has had a huge impact on local life, the area's indigenous Inuit people still rely heavily on the hunting of marine mammals, caribou, and fish. The Arctic National Wildlife refuge lies to the northeast, along the Yukon border.