Mount Toba created the giant caldera now occupied partly by Lake Toba in Sumatra.
The Toba volcanic system produced the Toba eruption, one of the largest known explosive eruptions of the Quaternary period. The eruption formed a vast caldera in northern Sumatra, which later filled with water to create Lake Toba. Samosir Island occupies part of the caldera and is itself a large resurgent feature.
The eruption is commonly dated to about 74,000 years ago. It spread ash and volcanic material over wide areas of Asia and left a thick ash deposit beneath the Indian Ocean. Scientists continue to study its environmental effects and possible influence on human populations.
Toba is sometimes described as a single cone, but it is more accurately a complex volcanic system and caldera. Lake Toba is the visible landscape left by that immense eruption.