Russian Empire Bolsheviks followed in 1918. The administrative boundaries of European Russia, apart from Finland and its portion of Poland, coincided approximately with the natural limits of the East-European plains. In the North it met the Arctic Ocean. Novaya Zemlya and the Kolguyev and Vaygach Islands also belonged to it, but the Kara Sea was referred to Siberia. To the East it had the Asiatic territories of the Empire, Siberia and the Kyrgyz steppes, from both of which it was separated by the Ural Mountains, the Ural River and the Caspian Sea — the administrative boundary, however, partly extending into Asia on
North Asia Urals, covering the northern two thirds of the Ob Basin and extending onto the Angara Shield between the Yenisei River and the Lena River. There are legacies of mountain glaciation to be found on the east Siberian mountains, on the mountains of the Kamchatka Peninsula, on the Altai, on Tian Shan, and on other small areas of mountains, ice caps remain on the islands of Severnaya Zemlya and Novaya Zemlya, and several Central Asian mountains still have individual glaciers. North Asia itself has permafrost, ranging in depths from 30 to 600 metres and covering an area of 9.6 million km².