PHIVOLCS issued special notices for Kanlaon noting periods of increased seismicity and continuing high levels sulfur dioxide gas emissions. The seismic network detected 288 volcano-tectonic earthquakes from 2030 on 9 September to 1100 on 10 September that were located at depths of 0-9 km beneath the NE flank. The strongest events were classified at Intensity II and felt in some barangays (neighborhoods) of Canlaon City, 8 km SSE, Negros Oriental. Rumbling sounds were reported by residents of Bago City and a strong sulfur odor was reported in a few barangays in the cities of Bago (30 km NW), La Carlota (14 km W), and Canlaon. According to a news article the intense seismicity prompted the local Canlaon City government to order a mandatory evacuation of the Permanent Danger Zone, defined as a 4 km radius from the summit, as a precautionary measure. About 91 families (301 people) moved to evacuation centers.

Summit emissions of sulfur dioxide measured with a Flyspec instrument averaged 9,985 tonnes/day (t/d) on 10 September, the highest ever recorded at the volcano. Sulfur odors were reported in the barangays of Ilijan (Bago), Ara-al and San Miguel (La Carlota), and in Masulog, Linothangan, and Pula (Canlaon). A steam-and-gas plume rose 1 km above the summit and drifted SE. Another record high for sulfur dioxide emissions was recorded on 11 September with an average of 11,556 t/d. Residents reported sulfur odors in areas downwind including San Miguel, Masulog, Pula, Codcod (San Carlos City), and Inolingan (Moises Padilla). A news report noted that both public and private schools suspended classes in four barangays.

Elevated sulfur dioxide gas fluxes had been recorded in 2024 with an average of 1,273 t/d prior to the 3 June eruption; afterward the eruption emissions were averaging 3,468 t/d. The Alert Level remained at 2 (on a scale of 0-5) and PHIVOLCS reminded the public to remain outside of the 4-km-radius Permanent Danger Zone and warned pilots not to fly close to the volcano.

Geological Summary. Kanlaon volcano (also spelled Canlaon) forms the highest point on the Philippine island of Negros. The massive andesitic stratovolcano is covered with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller but higher active vent, Lugud crater, to the south. Eruptions recorded since 1866 have typically consisted of phreatic explosions of small-to-moderate size that produce minor local ashfall.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Philippine News Agency (PNA), Philippine News Agency (PNA)