Yukon Plateau

a plateau in the northwestern part of North America. The Yukon Plateau, which occupies much of Alaska’s interior and the northwestern part of Canada, borders on the Brooks Range in the north, the Alaska Range and St. Elias Mountains in the south, the Mackenzie Mountains in the east, and the Bering and Chukchi seas in the west. It consists of large massifs that are separated by tectonic troughs. The mountains, which are deeply dissected by rivers, rise to elevations of 1,500–2,000 m; in the west, the floors of the intermontane basins are situated at elevations not exceeding 200 m, and in the southeast, at elevations not exceeding 500 m.

The plateau is composed of ancient, highly metamorphosed rocks with Mesozoic intrusions and sheets of younger volcanic rock. It has deposits of copper, lead, coal, tungsten, and gold. There is a highly branched system of rivers in the basins of the Yukon River (including the Tanana, Koyukuk, Porcupine, and Stewart rivers) and the Kuskokwim River; the rivers form broad meanders in the intermontane basins.

The region has a subarctic, continental climate. The average January temperatures range from −10° to −30°C, and the average July temperatures, from 10° to 15°C; the lowest recorded temperature is –64°C. The annual precipitation is about 300 mm. Permafrost occurs everywhere. Low willow-poplar flood-plain forests grow along the rivers, while coniferous forests of spruce and larch grow on the river terraces and mountain slopes. Above 400 m there is open woodland, which at 600–700 m is replaced by mountain tundra vegetation.