Toba t?b [key], largest lake of Indonesia, 448 sq mi (1,160 sq km), N Sumatra. Situated in a vast volcanic caldera that is 1,475 ft (450 m) deep and was formed by a tremendous eruption some 74,000 years ago, it is drained by the Asahan River. In the lake is Samosir, a large island (205 sq mi/531 sq km) that is linked to the mainland by an isthmus. The eruption of Toba is hypothesized by some scientists to have decimated the early human inhabitants of S Asia, but it is unclear what the extent of the devastating effects of the eruption were.

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