Lake Toba is located in the caldera of a supervolcano that erupted about 75,000 years ago.
The lake lies in North Sumatra, Indonesia, inside the broad depression left by the Youngest Toba supereruption. Modern estimates place that VEI 8 eruption at roughly 74,000 years ago, within the commonly rounded figure of 75,000 years.
The eruption was one of the largest known explosive events of the Quaternary Period. It released enormous quantities of ash and volcanic material, while the collapsed caldera later filled with water to form Lake Toba. The lake is about 100 kilometers long, up to 30 kilometers wide, and reaches roughly 505 meters in depth.
Samosir Island, a large island in the lake, is part of the volcanic landscape and includes uplifted caldera material. Scientists still debate how severely the eruption affected global climate and human populations, so claims that it nearly wiped out humanity should be treated as a theory rather than settled fact.