gently rolling plateau area of eastern Siberia, in Buryatiya and in Chita oblast (province), eastern Russia. The plateau is drained by the Vitim River and varies in height between 4,000 and 5,250 ft (1,200 and 1,600 m). It consists of a series of granites, granite-gneisses and gneiss-granites, while in the centre and southwest are basalts and basalt lavas extruded by numerous small and now extinct local volcanoes. The rivers have eroded canyon-like courses.