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How did Lake Tanganyika form in the East African Rift System?

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tectonic basins and rift valleys Escarpments of the Great Rift Valley rising above the plain north of Samburu Game Preserve, central Kenya. Beisa oryxes graze in the foreground.

Lake Tanganyika formed as a result of the geological processes defining the East African Rift System, a massive series of fissures in the Earth’s crust that has been developing for approximately 30 million years.12

The lake occupies the southern portion of the Western Rift Valley, which is a tectonic basin. These landforms are typically created by the extension of the crust, which causes it to fracture. As large crustal blocks diverge, a central block—known as a graben—slides downward into the resulting gap. This down-dropping process creates a deep, steep-sided trough.3

Because of this tectonic origin, Lake Tanganyika is exceptionally deep and fjordlike, with land rising steeply from its shores. The formation of the rift system has been accompanied by significant volcanic activity and the creation of various highlands and basins across eastern Africa.145