Their work, titled "Resurgence initiation and subsolidus eruption of cold carapace of warm magma at Toba Caldera, Sumatra," ...

On the very bad day in question, one particular volcano, now known as Mount Toba, had been active for a long time. It had bulged up gradually until it towered almost 3,000 feet above the jungle.

Exposure of explosive ash deposits tens of meters thick, 30 to 40 kilometers north of the Toba caldera. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases ...