Lake Baikal ( ; ; ) is a rift lake in Russia. It is situated in southern Siberia, between the federal subjects of Irkutsk Oblast to the northwest and the Republic of Buryatia to the southeast. At —slightly larger than Belgium—Lake Baikal is the world's seventh-largest lake by surface area. However, because it is also the deepest lake, with a maximum depth of , Lake Baikal is the world's largest freshwater lake by volume, containing of water or 22–23% of the world's fresh surface water, more than all of the North American Great Lakes combined. It is also the world's oldest lake at 25–30 million years, and among the clearest.
Lake Baikal is home to thousands of species of plants and animals, many of them endemic to the region. It is also home to Buryat tribes, who raise goats, camels, cattle, sheep, and horses on the eastern side of the lake, where the mean temperature varies from a winter minimum of to a summer maximum of . The region to the east of Lake Baikal is referred to as Transbaikalia or as the Transbaikal, and the loosely defined region around the lake itself is sometimes known as Baikalia. UNESCO declared Baikal a World Heritage Site in 1996.
Geography and hydrography
Lake Baikal is in a rift valley, created by the Baikal Rift Zone, where the Earth's crust is slowly pulling apart. At long and wide, Lake Baikal has the largest surface area of any freshwater lake in Asia, at , and is the deepest lake in the world at . The bottom of the lake is below sea level, but below this lies some of sediment, placing the rift floor some below the surface, the deepest continental rift on Earth.
In geological terms, the rift is young and active – it widens about 2 cm (0.8 in) per year. The fault zone is also seismically active; hot springs occur in the area and notable earthquakes happen every few years. The lake is divided into three basins: North, Central, and South, with depths about , , and , respectively. Fault-controlled accommodation zones rising to depths about separate the basins. The North and Central basins are separated by Academician Ridge, while the area around the Selenga Delta and the Buguldeika Saddle separates the Central and South basins. The lake drains into the Angara, a tributary of the Yenisey. Landforms include Cape Ryty on Baikal's northwest coast.
Baikal's age is estimated at 25–30 million years, making it the most ancient lake in geological history. It is unique among large, high-latitude lakes, as its sediments have not been scoured by overriding continental ice sheets. Russian, U.S., and Japanese cooperative studies of deep-drilling core sediments in the 1990s provide a detailed record of climatic variation over the past 6.7 million years.
Longer and deeper sediment cores are expected in the near future. Lake Baikal is the only confined freshwater lake in which direct and indirect evidence of gas hydrates exists.
The lake is surrounded by mountains; the Baikal Mountains on the north shore, the Barguzin Range on the northeastern shore and the Primorsky Range stretching along the western shore. The mountains and the taiga are protected as a national park. It contains 27 islands; the largest, Olkhon, is long and is the third-largest lake-bound island in the world. The lake is fed by as many as 330 inflowing rivers. The main ones draining directly into Baikal are the Selenga, the Barguzin, the Upper Angara, the Turka, the Sarma, and the Snezhnaya. It is drained through a single outlet, the Angara.
Regular winds exist in Baikal's rift valley.
Water characteristics
Baikal is one of the clearest lakes in the world. During the winter, the water transparency in open sections can be as much as , but during the summer it is typically . Baikal is rich in oxygen, even in deep sections, which separates it from distinctly stratified bodies of water such as Lake Tanganyika and the Black Sea.