The Volcanology and Geological Hazard Mitigation Center (PVMBG) reported on Friday that the lava dome of Mount Sinabung in Karo, North Sumatra, was growing each day due to the volcano's high level of activity.
An officer at the PVMBG's Mt. Sinabung observation post, Deri Alhidayat, said quick growth in the lava dome could result in an additional volume of 100,000 cubic meters per day; slower growth yielded less volume.
Data at the PVMBG showed that the volume of Mt. Sinabung's lava dome had increased from 3 million cubic meters on Wednesday to 3.1 million cubic meters the following day.
"Today, we cannot detect the growth of the lava dome because Mt. Sinabung has been covered in thick fog until this afternoon," Deri told The Jakarta Post on Friday, adding that the activity of the volcano was still high.
Deri said the speed of the growth of the lava dome depended on the volcano's activity. The higher the activity, the bigger the growth.
As of Friday at noon, Deri said, his post had detected low frequency volcanic earthquakes and 106 avalanche earthquakes from Mt. Sinabung.
As of 6 a.m. on the same day, the volcano was detected to have spewed lava five times, which slid down its slopes for a kilometer to the south and 1.5 km to the southeast.
"It's feared that these small avalanches of lava will trigger bigger avalanches. Caution is needed in this situation," Deri said.
Asked whether the situation would affect the PVMBG's recommendation regarding the radius of the areas to be evacuated, Deri said the current recommendation of 7 km had included 1 km to anticipate a bigger volume of lava.
He said that with a volume of 3 million cubic meters, the lava could reach 6 km down the slope of the volcano. That way, the 7-km radius recommendation was considered safe.
"But if the growth of the lava dome continues, it is possible that the recommended radius for the dangerous zone will increase," Deri said.
The PVMBG had since Tuesday night increased the alert status of Mt. Sinabung to the highest level and recommended that people residing within a radius of 7 km from the crater of the volcano were evacuated.
As many as 2,727 people or 677 families were reported to have evacuated since then. They came from four subdistricts located to the south and southeast of the crater of Sinabung.
Karo Regent Terkelin Brahmana said that so far the evacuees' needs for basic necessities had been fulfilled from the regency budget and private sector resources.
Separately, Karo Disaster Mitigation Agency (BPBD) head Subur Tambun said the agency was temporarily using ready-to-spend funds from the National Disaster Mitigation Agency (BNPB) from last year's remaining budget of Rp 80 million (US$6,000) to fulfil evacuees' needs for basic necessities for the next few weeks.