Mount Sinabung in North Sumatra province, the Indonesian volcano which was dormant for four centuries, erupted for the second straight day on Monday.
As a result it shot clouds of hot ash more than a mile into the air, forced 30,000 people to flee and required domestic airplanes to be diverted because of poor visibility.
Villagers living along the slopes packed their belongings and headed to emergency shelters, mosques and churches. The government has 16 shelters housing 21 000 displaced people.
What they left behind was blanketed in gray soot and the air was thick with the smell of sulfur.
Two people have died so far. A 64-year-old woman from respiratory problems and a 52-year-old man from a heart attack.
Sinabung’s last erupted was in 1600, so observers don’t know its eruption pattern and admitted over the weekend they had not monitored it closely before it started rumbling days ago in the lead-up to Sunday’s first, less-powerful blast.
Hours later, the alert was raised to the highest level.
Like other volcanoes along the Sumatra fault line — the meeting point of the Eurasian and Pacific tectonic plates that have pushed against each other for millions of years.
It has the potential to be very destructive.
Stiff magna forming inside the conical tip can act as a plug, allowing pressure to build up until it reaches a bursting point.
“A volcano with a long repose period could deliver a more powerful eruption,” as was the case with Pinatubo in the Philippines in 1991, which killed about 800 people, said Alain Bernard, a professor at the University of Brussels.
Sinabung could either go back to sleep or produce a series of blasts with increasing intensity, he said. “A Pinatubo-size eruption is a rare event and unlikely to appear during the following days. It takes normally weeks or months,” said Bernard.