MANILA, Philippines — The Philippine Institute of Volcanology and Seismology (Phivolcs) raised Alert Level 1 over Bulusan Volcano in Sorsogon yesterday amid its heightened activity.
“Bulusan Volcano entered a period of low-level unrest with a sustained series of volcanic earthquakes that began on Oct. 14,” Phivolcs said.
At least 121 volcanic earthquakes have been recorded since Oct. 14, 37 of which were associated with rock fracturing processes at depths of one to nine kilometers beneath the northwestern and southeastern slopes of the volcano edifice.
Phivolcs said swelling of the southern flank has been observed since February and the northeastern flank since September.
A notable increase of volcanic carbon dioxide concentrations from June to August and spring temperature since February were detected on the southwestern slopes.
Phivolcs said 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.
Phivolcs reminded concerned local government units and the public that entry into the four-kilometer-radius permanent danger zone is prohibited. Vigilance in the two-kilometer extended danger zone in the southeast sector should be exercised due to increased possibilities of sudden and hazardous phreatic eruptions from the summit crater or lateral vents, it added.
Civil aviation authorities should advise pilots to avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft.
The last time Bulusan was placed under Alert Level 1 was on Oct. 12 last year. The alert level was downgraded to zero on Jan. 18.