The Philippine Institute of Volcanology and Seismology (PHIVOLCS) has issued a notice of increased seismic activity at Kanlaon Volcano, with a total of 41 volcano-tectonic (VT) earthquakes recorded in a 13-hour period.
According to a PHIVOLCS advisory released today, September 14, the Kanlaon Volcano Network registered the earthquakes between 11:00 PM yesterday and 10:00 AM today. These events, ranging in strength from ML0.8 to ML 4.6, were generated at depths of 0 to 7 kilometers beneath the northwestern flanks of the volcano.
The strongest of these VT earthquakes, with a magnitude of 4.6, was felt at Intensity III in several areas, including La Carlota City and Bacolod City in Negros Occidental, Canlaon City in Negros Oriental, and the localities of Bago City, Murcia, and La Castellana in Negros Occidental. The information on the felt shaking was based on reports from social media.
PHIVOLCS explained that VT earthquakes are caused by rock fracturing processes. The recent increase in this activity “strongly indicates progressive rock-fracturing beneath the volcano as rising magma or magmatic gas drives a path towards the surface.”
While the seismic activity has intensified, volcanic sulfur dioxide (SO_2) gas emissions from the summit crater have been measured at an average of 1,122 tonnes/day, lower than the medium-term average of 2,594 tonnes/day since January 1, 2025. PHIVOLCS noted that this blockage of gas emission, or “closed-system degassing,” could lead to “pressurization and swelling of the edifice potentially leading to a moderately explosive eruption.”
Alert Level 2 Remains in Effect
Kanlaon Volcano remains under Alert Level 2, indicating a state of “increased unrest.” The public is reminded that the rise in VT events could increase the chances of “steam-driven or phreatic eruptions or short-lived weak to moderately explosive eruptions” at the summit.
These eruptions could generate life-threatening volcanic hazards such as pyroclastic density currents (PDCs), ballistic projectiles, ashfall, and rockfall.
Authorities are strongly recommending that communities within the 4-kilometer Permanent Danger Zone (PDZ) remain evacuated. Additionally, those within a 6-kilometer radius of the summit crater are advised to be vigilant and prepared in case the unrest escalates.
PHIVOLCS also warned of the potential for syn-eruption lahars and sediment-laden streamflows in channels draining the volcano, especially if intense rains occur during the unrest. Civil aviation authorities are urged to advise pilots to avoid flying close to the volcano’s summit, as sudden eruptions could release ash hazardous to aircraft.
