Lake Baikal - Geography and Hydrography

Geography and Hydrography

The Trans-Siberian railway was built between 1896 and 1902. Construction of the scenic railway around the southwestern end of Lake Baikal required 200 bridges and 33 tunnels. Until its completion, a train ferry transported railcars across the lake from Port Baikal to Mysovaya for a number of years. At times during winter freezes, the lake could be crossed on foot—though at risk of frostbite and deadly hypothermia from the cold wind moving unobstructed across flat expanses of ice. A mass-crossing of military-historical significance, which did indeed leave many dead from cold-exposure was the 1920 Great Siberian Ice March. Beginning in 1956, the impounding of the Irkutsk Dam on the Angara River raised the level of the lake by 1.4 m (4.6 ft).

As the railway was built, a large hydro-geographical expedition headed by F.K. Drizhenko produced the first detailed contour map of the lake bed.

Lake Baikal is in a rift valley, created by the Baikal Rift Zone, where the Earth's crust pulls apart. At 636 km (395 mi) long and 79 km (49 mi) wide, Lake Baikal has the largest surface area of any freshwater lake in Asia, at 31,722 km2 (12,248 sq mi), and is the deepest lake in the world at 1,642 m (5,387 ft). The bottom of the lake is 1,186.5 m (3,893 ft) below sea level, but below this lies some 7 km (4.3 mi) of sediment, placing the rift floor some 8–11 km (5.0–6.8 mi) below the surface: the deepest continental rift on Earth. In geological terms, the rift is young and active—it widens about two cm per year. The fault zone is also seismically active; there are hot springs in the area and notable earthquakes every few years. The lake is divided into three basins: North, Central, and South, with depths of about 900 m (3,000 ft), 1,600 m (5,200 ft), and 1,400 m (4,600 ft), respectively. Fault-controlled accommodation zones rising to depths of about 300 m (980 ft) 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 tributary of the Yenisei. There is Cape Ryty on Baikal's northwest coast.

Baikal's age is estimated at 25–30 million years, making it one of the most ancient lakes in geological history. It is unique among large, high-latitude lakes, in that its sediments have not been scoured by overriding continental ice sheets. U.S. and Russian studies of core sediment in the 1990s provide a detailed record of climatic variation over the past 250,000 years. Longer and deeper sediment cores are expected in the near future. Lake Baikal is furthermore the only confined fresh water lake in which direct and indirect evidence of gas hydrates exists.

The lake is completely surrounded by mountains. The Baikal Mountains on the north shore and the taiga are technically protected as a national park. It contains 27 islands; the largest, Olkhon, is 72 km (45 mi) long and is the third-largest lake-bound island in the world. The lake is fed by as many as three hundred and thirty inflowing rivers. The main ones draining directly into Baikal are the Selenga River, the Barguzin River, the Upper Angara River, the Turka River, the Sarma River and the Snezhnaya River. It is drained through a single outlet, the Angara River.

Despite its great depth, the lake's waters are well-mixed and well-oxygenated throughout the water column, compared to the stratification that occurs in such bodies of water as Lake Tanganyika and the Black Sea.