Increased seismicity observed in Kanlaon Volcano; alert Level 3 stays

(File Photo: UNREST. A thick plume generated by Mt. Kanlaon’s eruption on Tuesday morning (April 8, 2025). Phivolcs said the volcano’s explosive eruption was a result of gas pressure. (Screengrab via Philippine Institute of Volcanology and Seismology (PHIVOLCS-DOST)/Facebook)

By Ma. Cristina Arayata, Philippine News Agency

MANILA – The Philippine Institute of Volcanology and Seismology (Phivolcs) reported an increase in Kanlaon Volcano’s seismic activity on Monday.

Seventy-two volcanic earthquakes were recorded from 12 a.m. to 12 p.m. Their magnitudes ranged from 0.3 to 3.1, and were 0 to 8 kilometers deep beneath the northern and northwestern flanks of the volcanic edifice.

Phivolcs said 135 volcanic earthquakes were recorded since 12 a.m. of May 11, and these included relatively strong volcano-tectonic (VT) earthquakes.

VTs are generated by rock fracturing processes and the increase in VT activity strongly indicates progressive rock fracturing beneath the volcano as rising magma or magmatic gas drives a path towards the surface.

Meanwhile, sulfur dioxide (SO2) gas emissions from the summit crater measured 554 tons on May 11.

There has been a decline in the average SO2 emission from 4,144 since June 3, 2024 to 2,114 since April 1, 2025.

“The parameters indicate that the blockage of volcanic gas emission (or closed-system degassing) may result in pressurization and swelling of the edifice potentially leading to moderately explosive eruption at Kanlaon,” Phivolcs said in an advisory on Monday afternoon.

Earlier, Phivolcs said it is generally safe for people to cast their votes, but noted communities near Kanlaon Volcano, currently under alert Level 3 or magmatic unrest, must stay outside the 6-kilometer danger zone.

At alert Level 3, there are increased chances of short-lived moderately explosive eruptions occurring that could generate life-threatening volcanic hazards.

Local government units are advised to continue preparing their communities within the pyroclastic density currents hazard zone for subsequent evacuation in case unrest further escalates and a hazardous worst-case explosive eruption becomes imminent, Phivolcs said.

“Increased vigilance against potential syn-eruption lahars and sediment-laden streamflows in channels draining the edifice is strongly advised should intense rains occur during eruptive unrest,” it added.

Aviation authorities must advise pilots to avoid flying close to the volcano’s summit as ash from any sudden eruption can be hazardous to aircraft, Phivolcs said.