The explosive outburst in what is now Peru was much bigger than scientists had realized.

Scientists re-examining a South American volcano’s 1600 eruption have found that it was among the biggest of its kind in the world over the past two millennia.

In 1600, the Huaynaputina volcano in the Andes Mountains in southern Peru buried nearby villages, killing around 1,500 people, and hurled enough Sun-blocking particles into the atmosphere to cool the planet. Researchers classify the event as an explosive ‘Plinian’ eruption, and have long thought it to be the largest eruption in South America since 1540.

Jean-Marie Prival at the University of Clermont Auvergne in Clermont-Ferrand, France, and his colleagues reassessed the eruption’s size by mapping ash and rock from the 1600 event. The team calculated that the volcano expelled up to 14 cubic kilometres of material, nearly twice as much as scientists had thought. That makes the 1600 cataclysm one of the largest Plinian eruptions on Earth in the past 2,000 years.

Huaynaputina has not erupted for centuries. But if it were to erupt on a similar scale today, up to 12 million people in Peru, Bolivia and Chile would be affected, the scientists say.