IROSIN, SORSOGON: Over 1,000 people were evacuated in the towns of Irosin and Juban for safety after disaster authorities in Sorosogn province braced for the worst from a restive Mount Bulusan, and the possibility of Tropical Storm Dodong developing into a supertyphoon.
The Philippine Institute of Volcanology and Seismology (Phivolcs) has raised the alert status of Mount Bulusan in Sor-sogon from normal to Alert Level 1, after it spewed ash plume cloud as high as 250 meters, spawned by a phreatic eruption, on Wednesday night.
Alert Level 1 indicates Bulusan Volcano continues to show signs of restiveness after it ejected ash clouds for the third time at about 9:30 p.m. Wednesday, Phivolcs said.
Ed Laguerta, Phivolcs resident volcanologist, said the agency had to raise the volcano’s level to 1 from normal because hydrothermal abnormalities beneath the volcano may lead to more steam-driven or phreatic eruptions in the coming days.
Phivolcs director Renato Solidum warned disaster responders and the public to be on guard because Bulusan volcano many unleash a series of explosions soon.
“Bulusan eruption is different from Mayon volcano. Usually Bulusan is steam-driven explosion and the last magmatic explosion occurred 40 years ago,” he said.
“Due to pressure build-up, the steam escapes through the crater explosively. Such explosions are typical to Bulusan during restive periods, when its hydrothermal system is disturbed or when steam accumulates and pressurizes at the shallow levels of the volcanic edifice,” Solidum said.
This indicates that hydrothermal processes may be underway beneath the volcano that may lead to more steam-driven eruptions. The explosion event lasted for 3.5 minutes based on the seismic records. Traces of ash were observed in Sitio (sub-village) Tulay of barangays (village) Bagsangan, Cogon, Monbon, and Tinampo in Irosin, Sorsogon.