TANAH KARO, Indonesia — Tens of thousands of people packed emergency shelters Monday after a long-dormant volcano in western Indonesia spewed clouds of hot ash and smoke more than a mile into the air — an eruption that caught scientists off-guard.
The eruption of Mount Sinabung put the region on the highest alert level, and some domestic flights had to be diverted because of poor visibility.
Villagers living along Sinabung’s fertile slopes in North Sumatra province started heading down the 8,000-foot volcano after it began rumbling during the weekend.
An explosion Sunday was followed by a much more powerful blast Monday. The number of people who evacuated hit 30,000, with hastily abandoned homes and crops blanketed in gray ash. The air was thick with the smell of sulfur.
Two people died, but Priyadi Kardono of the National Disaster Management Agency said it was too early to say whether the volcano was to blame.
Sinabung last erupted in 1600, and officials acknowledged that they had not been monitoring the volcano because it had been dormant for so long.
“The nearest monitoring post to Sinabung is Mount Merapi — around 400 kilometers to the southeast — so we were totally in the dark,” said Imam Simulingga, a government vulcanologist. “We didn’t know anything until it started rumbling.”
Monitoring a volcano can include such techniques as looking for seismic activity that indicates disturbances from rising magma, sampling gases and looking for slight degrees of uplift in land, said Lee Siebert, director of the Global Volcanism Program at the Smithsonian Institution.
He said it is no surprise that Sinabung would erupt after 400 years of being quiet. That’s not very long by geological standards, Siebert said, noting that a volcano that has erupted within the past 10,000 years can be considered active.
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 — Sinabung has the potential to be very destructive. Magma forming inside the conical tip can act as a plug, allowing pressure to build until it reaches a bursting point.
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Active volcanoes in Indonesia
Indonesia’s volcanoes
Indonesia is spread across 17,500 islands and is prone to eruptions and earthquakes because of its location within the “Ring of Fire” — a series of fault lines stretching from the Western Hemisphere through Japan and Southeast Asia.
Indonesia is home to some of the largest eruptions in recorded history. The 1815 explosion of Mount Tambora buried the inhabitants of Sumbawa Island under searing ash, gas and rock, killing an estimated 88,000 people.
The Associated Press
