Lake Baikal, located in southern Siberia, Russia, is the world’s deepest and oldest freshwater lake, with an estimated age of 25 to 30 million years. This vast body of water contains approximately 22-23% of the planet’s fresh surface water, a volume greater than all of North America’s Great Lakes combined. Its exceptional clarity allows visibility up to 40 meters in winter.
The Deepest Point and Geological Origins
Lake Baikal’s maximum depth plunges to 1,642 meters (5,387 feet). The bottom of the lake itself lies approximately 1,186.5 meters below sea level. This profound depth is a direct consequence of its formation within an active rift valley, where the Earth’s crust is slowly pulling apart. The Baikal Rift Zone is an ongoing geological process, causing the lake to widen by about 4 millimeters annually.
This active rifting has created a unique geological structure, more akin to an ocean basin in its development than a typical lake. Below the lakebed, layers of sediment extend for an additional 7 kilometers, pushing the rift floor to a depth of 8 to 11 kilometers (5 to 7 miles) below the surface. This makes Lake Baikal’s underlying geological rift the deepest continental rift on Earth. The vast accumulation of these sedimentary strata over millions of years provides a comprehensive record of the region’s climate history.
Unique Life Forms of the Abyssal Zone
The deep-water (abyssal) zones of Lake Baikal’s bottom harbor a unique array of life, characterized by a high degree of endemism. Over 80% of the lake’s 2,500 animal species are found nowhere else on Earth. This biological uniqueness has led to Lake Baikal being referred to as the “Galapagos of Russia.” The lake’s deep waters are rich in oxygen, a characteristic that differentiates it from other deep, stratified water bodies and allows for a diverse deep-water fauna.
Among the unique inhabitants are specialized sponges of the family Lubomirskiidae. These freshwater sponges have adapted to extreme thermal ranges and high pressure. The lake is also home to over 350 species of amphipods, small shrimp-like crustaceans, with about 80% of the world’s freshwater amphipods residing here. Some, like the spiny Acanthogammarus, can reach up to 7 cm in length. The Baikal seal, or nerpa, is the only mammal inhabiting the lake, capable of diving to considerable depths in search of food.
Exploring the Bottom
Scientific exploration of Lake Baikal’s depths has progressed with the use of submersibles and other technologies. The Russian Mir submersibles, Mir-1 and Mir-2, conducted investigations in the lake during 2008 and 2009. These submersibles performed over 120 dives, reaching depths exceeding 1,680 meters, which marked the deepest freshwater dives ever undertaken.
These expeditions led to discoveries, including the presence of large deposits of methane hydrates. These icy formations, consisting of methane gas trapped in water molecules, were found at certain sites, notably at mud volcanoes and gas seep fields. The Mir submersibles also surveyed hydrothermal vents, which release water at temperatures around 50°C, and provided insights into the lake’s geological activity. These explorations have contributed to a better understanding of Baikal’s tectonic processes, its climate history, and its unique deep-water ecosystems.