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Western Siberian plain Seen from the Trans-Siberian railway outside Tatarskaya

The West Siberian Plain (Russian: За́падно-Сиби́рская равни́на) is a large plain that occupies the western portion of Siberia in Russia, between the Ural Mountains in the west and the Yenisei River in the east, and by the Eastern Sayan Mountains and the Baikal Mountains on the south. It has been described as the world's largest unbroken lowland—more than 50 percent is less than 330 feet (101 m) above sea level^[1]—and covers an area of about 2.6–2.7 million km² which is about one third of Siberia,^[2] extending from north to south for 2,400 km, from the Arctic Ocean to the foothills of the Altay Mountains, and from west to east for 1,900 km from the Yenisei River to the Ural Mountains.

The plain has eight distinct vegetation regions: tundra, forest-tundra, northern taiga, middle taiga, southern taiga, sub-taiga forest, forest-steppe, and steppe. The number of animal species in the West Siberian Plain ranges from at least 107 in the tundra to 278 or more in the forest-steppe region.

Winters on the West Siberian Plain are harsh and long. The climate of most of the plains is either subarctic or continental. Two of the larger cities on the plain are Surgut and Nizhnevartovsk.

The West Siberian Plain consists mostly of Cenozoic alluvial deposits and is extraordinarily flat. A rise of fifty metres in sea level would cause all land between the Arctic Ocean and Novosibirsk to be inundated (see also Turgai Straits, West Siberian Glacial Lake). Many of the deposits on this plain result from ice dams; having reversed the flow of the Ob and Yenisei Rivers, redirecting them into the Caspian Sea, and perhaps the Aral Sea as well. It is very swampy and soils are mostly peaty Histosols and, in the treeless northern part, Histels.

It is one of the world's largest areas of peatlands, which are characterized by raised bogs. It is believed that the world’s largest single raised bog is at Vasuganskoe, covering approximately 51,600 km².

In the south of the plain, where permafrost is largely absent, rich grasslands that are an extension of the Kazakh Steppe formed the original vegetation (almost all cleared now).

Large regions of the plains are flooded in the spring, and marshlands make much of the area unsuitable for agriculture. The principal rivers in the West Siberian Plain are the Ob, Irtysh, and Yenisei. There are many lakes and swamps, as well as large petroleum and natural gas reserves. Most of the Russia's oil and gas production was extracted from this area during the 1970s and 80s.^[2]

• East European Plain, the other major plain of Russia
• Eurasian steppe

• West Siberian Plain
• Topography and Drainage of Russia
• Peatlands of the Worls: Russia — Siberia

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