Bulusan Volcano placed under Alert Level 1 —Phivolcs

The Philippine Institute of Volcanology and Seismology (Phivolcs) on Wednesday raised Bulusan Volcano’s alert status from Alert Level 0 to Alert Level 1, which means low-level unrest.

“Bulusan Volcano entered a period of low-level unrest with a sustained series of volcanic earthquakes that began on 14 October 2023,” Phivolcs said in its 3 p.m. advisory.

“Since then, a total of one hundred twenty-one (121) volcanic earthquakes have been recorded by the Bulusan Volcano Network (BVN),” it added. 

Phivolcs said 37 of these were volcano-tectonic earthquakes linked to rock fracturing processes, which are 1-9 kilometers under the northwestern and southeastern slopes of the volcano edifice.

Inflation or swelling of the southern flank has been observed since February 2023 and of the northeastern flank since September 2023, according to Phivolcs.

There was an increase in the volcanic carbon dioxide concentrations from June to August 2023 and spring temperature since February 2023 in a monitored spring on the southwestern slopes.

According to Phivolcs, these developments may lead to steam-driven eruptions at any of Bulusan’s summit vents.

“These parameters indicate that hydrothermal activity driven by deep-seated magma degassing may be occurring beneath the volcano and may lead to steam-driven eruptions at any of its summit vents,” it said.

Phivolcs reminded that entry into the four-kilometer radius Permanent Danger Zone (PDZ) should be prohibited.

In the two-kilometer Extended Danger Zone (EDZ) in the southeast sector, Phivolcs said vigilance must be exercised due to “increased possibilities of sudden and hazardous phreatic eruptions from the summit crater and/or lateral vents.”

Pilots should avoid flying close to the volcano's summit as ash from any sudden phreatic eruption can be hazardous to aircraft.

Residents within the valleys and along rivers/stream channels, especially on the southeast, southwest, and northwest sectors of the edifice should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall should a phreatic eruption occur, Phivolcs said. —Joviland Rita/ VAL, GMA Integrated News