Youngest Toba eruption

The Toba eruption (also called the Toba supereruption and the Youngest Toba eruption) was a large eruption that occurred around 74,000 years ago, during the Late Pleistocene, at the site of present-day Lake Toba, in Sumatra, Indonesia. It was the last in a series of at least four caldera-forming eruptions there, the earlier known caldera having formed about 1.2 million years ago. This, the last eruption, had an estimated volcanic explosivity index of 8, making it the largest known explosive volcanic eruption in the Quaternary, and one of the largest known explosive eruptions in the Earth's history.

Eruption

Chronology of the Toba eruption

The exact date of the eruption is unknown, but the pattern of ash deposits suggests that it occurred during the northern summer because only the summer monsoon could have deposited Toba ashfall in the South China Sea. The eruption lasted perhaps 9 to 14 days. The most recent two high-precision argon–argon datings dated the eruption to 73,880 ± 320 and 73,700 ± 300 years ago. Five distinct magma bodies were activated within a few centuries before the eruption. The eruption commenced with small and limited air-fall and was directly followed by the main phase of ignimbrite flows. The ignimbrite phase is characterized by low eruption fountain, but co-ignimbrite column developed on top of pyroclastic flows reached a height of 32 km (20 mi). Petrological constraints on sulfur emission yielded a wide range from 1×1013 to 1×1015 g, depending on the existence of separate sulfur gas in the Toba magma chamber.