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The Philippine Institute of Volcanology and Seismology (Phivolcs) raised Alert Level 1 over Bulusan Volcano on Wednesday.

In its 3 pm bulletin, Phivolcs said it raised the alert level because the volcano “entered a period of low-level unrest with a sustained series of volcanic earthquakes” since October 14.

The Bulusan Volcanic Network has recorded 121 volcanic earthquakes, 37 of which are tectonic and are linked to rock fracturing processes at depths of one to nine kilometers beneath the northwestern and southeastern slopes of the volcano edifice.

Phivolcs recorded a significant increase in carbon dioxide from June to August and spring temperature since February was detected in a monitored spring on the southwestern slopes.

“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 said.

Phivolcs reminded local government units and the public not to enter the four-kilometer Permanent Danger Zone and that they should be careful of the two-kilometer Extended Danger Zone in the southeast sector “due to increased possibilities of sudden and hazardous phreatic eruptions from the summit crater and/or lateral vents”.

Civil aviation authorities are also reminded to warn pilots from flying near Bulusan Volcano’s summit since ash from any sudden phreatic eruption could be dangerous to the plane. Jaspearl Tan/DMS