 The Amur–Zeya and Zeya–Bureya Plains cover about 40% of the oblast's territory, but the rest is hilly.Several mountain ranges rise to the south of Stanovoy Range, including the Selemdzha Range parallel to it, as well as the Ezop, Jam-Alin and the Turan ranges stretching along the oblast's southeastern border with Khabarovsk Krai.Many rivers flow through the oblast, especially in the north, accounting for 75% of the hydropower resources in the Russian Far East.