Lake Tanganyika
The world's longest freshwater lake and second deepest
Tanganyika is a sliver of water improbably long and improbably deep — a ribbon stretching 673 kilometres down the floor of the Western Rift, making it the longest freshwater lake on Earth and, after Baikal, the second deepest. It is also among the oldest lakes anywhere, its waters having stood in the rift for millions of years, time enough for an extraordinary cast of fish and snails to evolve nowhere else. Four nations share its shores, and beneath its surface lies a still, dark, oxygen-starved abyss that has never seen the sun.
The lake fills a crack where the African continent is slowly tearing itself apart, which is why it plunges to 1,471 metres while measuring only a few dozen kilometres across. Below about 100 metres the water holds almost no oxygen and almost never mixes with the layers above, so life concentrates in a thin sunlit band near the top. Within that band swim some 250 species of cichlid fish, most of them found only here, alongside endemic crabs and shells. The lake drains, intermittently and weakly, toward the Congo River and ultimately the Atlantic.
Explorers Richard Burton and John Speke became the first Europeans to record the lake in 1858, and a decade later Henry Morton Stanley met David Livingstone on its eastern shore at Ujiji. During the First World War its waters saw a strange naval campaign immortalised in fiction and film. Today Tanganyika supports a vital sardine-like fishery feeding the populations of Tanzania, the Democratic Republic of the Congo, Burundi, and Zambia, even as overfishing and a warming surface threaten the productivity of one of the planet's great freshwater treasures.