Siberia's administrative units are the Altay, Buryat, Khakass, and Tuva republics, the Altay and Krasnoyarsk territories, the Omsk, Novosibirsk, Tomsk, Kemerovo, Irkutsk, and Chita regions, and the Taimyr, Ust-Ordyn-Buryat, and Evenki autonomous areas. Lying off Siberia in the Arctic Ocean are the New Siberian Islands, the Severnaya Zemlya Archipelago, and other islands.
Siberia may be divided, from north to south, into the zones of vegetation that run across Russia - the tundra, the taiga, the mixed forest belt, and the steppe zone. Forests occupy about 40% of Siberia's land. Siberia is drained, from south to north, by the Ob, Yenisei, and Lena rivers (and their tributaries), which also provide the only means of longitudinal transportation.
These rivers empty northward into the Arctic Ocean. East-west transportation depends largely on the Trans-Siberian Railway (which follows the steppe belt), on the Baikal-Amur Mainline (BAM), and to an increasing extent on the Arctic sea route.
Siberia is conventionally subdivided into the following four geomorphologic areas: the West Siberian lowland; the Central Siberian plateaus, or uplands; the mountains of the south; and the northeast Siberian mountain systems.
The lowland occupies the western third of Siberia; it stretches from the Urals to the Yenisei and is mainly a low-lying, often marshy, plain. It is drained by the Ob and Irtysh rivers, which are ice-free and navigable for about half the year. Situated far from vulnerable frontiers, South-Western Siberia contains about 60% of Siberia's population, major industrial complexes, and such important cities as Novosibirsk (the leading industrial and scientific research centre of Siberia), Omsk, Tomsk, Tobolsk, Barnaul, and Novokuznetsk.
The wooded steppe and fertile black earth of Western Siberia favour agriculture and, especially in the Baraba Steppe, dairying. Wheat is the principal crop; rye, oats, potatoes, sunflowers, flax, and sugar beets are also important.
Butter is the major dairy product. The Kuznetsk Basin, in Western Siberia, is one of the world's richest coal regions and also has modest iron deposits. It forms the basis for the region's iron, steel, and heavy metallurgical industries. Rich oil and natural-gas fields have been exploited in the West Siberian lowlands, from which a network of pipelines now serves European Russia and the Eastern European republics.
Eastern Siberia, which is drained by the Lena, extends from the Yenisei to a huge mountain chain, an offshoot of the mountains of Central Asia. South of the uplands lies Lake Baikal, the world's deepest lake, surrounded by mountains.
Eastern Siberia's important cities include Krasnoyarsk, Irkutsk, Ulan-Ude, Cheremkhovo, Yakutsk, and Chita; but most of the region is sparsely populated because of the extreme rigors of the climate and the difficulties of communication.
Verkhoyansk, the coldest permanently inhabited settlement on earth (-56°F/-49°C on average in winter) has summer hot spells where the temperature rises above 90°F (32°C).
Eastern Siberia is Russia's leading producer of gold, diamonds, mica, and aluminium, and there are large reserves of iron ore, coal, oil, gas, graphite, and nonferrous precious metals.
Exploitation of the region's rich waterpower resources began in the mid-1950s, and there are four giant hydroelectric power stations on the Angara River between Irkutsk and Lake Baikal. Forestry, like mining, is a major economic activity in Eastern Siberia.
Agriculture is practiced in the south, and animal husbandry is prevalent among the indigenous Siberian peoples. Reindeer breeding, fishing, sealing, hunting, and fur processing are important occupations in the Arctic north.