Jakarta. The government says it will keep Mount Merapi and Mount Bromo at the highest alert level despite a significant decrease in volcanic activity at the two locations.
Merapi, located in Central Java, began erupting on Oct. 26. Officials estimate 324 people have died in the eruptions. Bromo, in East Java, began erupting a month later, but no casualties have been reported.
Volcanic activity at both locations has since diminished considerably, enough for the government to draw back the exclusion zone around Merapi’s crater.
Raden Sukhyar, head of the Energy and Mineral Resource Ministry’s geological division, said on Wednesday that the scale of the eruptions at the volcanoes provided a rare opportunity for Indonesian scientists to study the phenomenon firsthand.
“It’s true that volcanic activity at both Merapi and Bromo has subsided, but there are still so many things to learn,” he said.
He said that scientists were particularly interested in Merapi, which on Nov. 5 threw ash more than 10 kilometers into the atmosphere, making it the volcano’s biggest eruption in more than a century.
“This type of volcanic activity is something we cannot predict,” Sukhyar said. “Everything’s very strange to us, it’s a totally new experience, which is why we need to be extra careful and study it more.”
He added that the Merapi eruptions this year differed from those in 2006.
Prior to October’s eruptions, he said, Merapi was known more for its pyroclastic flows, or fast-moving clouds of superheated ash and gas, rather than its lava flows.
These latest eruptions, he said, have called into question many of the things scientists thought they knew about the volcano.
“The map of the danger zone around the mountain will definitely have to be redrawn once this is all over,” Sukhyar said.
“We can’t let people return to their homes on the slopes without knowing for sure whether they’ll be safe from future eruptions, so it’s better to wait.”
When the eruptions began, the government declared a 10-kilometer exclusion radius around the crater. But in early November, an eruption destroyed villages up to 18 kilometers away.
Surono, head of the Volcanology and Geological Disaster Mitigation Agency (PVMBG), said his office was still carefully monitoring Merapi, including the deformation of its crater and the ongoing seismic activity.
“We really can’t say when the alert status can be downgraded,” he added.
Volcanologists are also continuing to observe Bromo, where volcanic activity has fallen off since Friday. A three-kilometer exclusion zone is still in place and the mountain, part of the Bromo Tengger Semeru National Park, remains closed to visitors.
Sukhyar said it was unlikely volcanic activity at Bromo would pick back up again, but that the government did not want to take any chances.
“When dealing with a natural phenomenon, so a timeframe of a couple of days is nothing, it’s too short,” he said. “We need more time to study the situation.”
He said scientists would need at least a week to be able to detect a pattern of change in volcanic activity.