vast upland area, north-central Siberia, Russia. The plateau occupies an area of 600,000 square miles (1,500,000 square km). It is situated in Krasnoyarsk kray (region), Sakha, and in Irkutsk oblast (province). It is bounded by the Yenisey River to the west, the North Siberian Lowland to the north, the Lena River (according to some authorities, by the Verkhoyansk Mountains) to the east, and the Vostochny Sayan (Eastern Sayan) Mountains and the Baikal region to the south. The plateau is underlain by crystalline rocks of the stable Siberian Platform, but these are overlain by marine deposits as well as newer rock series. The average elevation is 1,650–2,300 feet (500–700 metres), but occasional tablelands occur: the Putoran Mountains, the Yenisey Ridge, and others. Vegetation in the plateau varies from tundra in the north to steppe-grasslands in the south.