A moderate explosive eruption at Kanlaon Volcano on Thursday night, followed by renewed ash emissions on Friday morning, has sent ashfall and sulfuric smell across 137 barangays in 18 towns and cities in Negros Occidental.
Affected by the falling ash are the municipalities of La Castellana, San Enrique, Murcia, Hinigaran, Moises Padilla, Binalbagan, Isabela, Pontevedra, Ilog, Hinoba-an, Candoni and Cauayan, as well as the cities of La Carlota, San Carlos, Bago, Himamaylan, Kabankalan, and Sipalay, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported on Friday, Feb. 27.
Sulfuric smell was also reported in some areas close to the volcano.
The Provincial Disaster Risk Reduction and Management Office said 23 families — comprising 81 individuals — evacuated in La Carlota City and La Castellana.
Twelve towns and cities ordered the suspension of classes on Friday as a safety precaution.
The Department of Education said 134,306 learners were affected by the suspension of classes.
The moderately explosive eruption began at 7:04 p.m. Thursday, during which Kanlaon spewed fire and ash for approximately two minutes.
A dark gray plume rose 2,500 meters above the vent before drifting southwest, generating volcanic lightning within the plume at least three times, Phivolcs added.
The explosion launched incandescent ballistic fragments as high as 1.5 kilometers from the summit crater, landing up to 1.5 kilometers away on the southeast and south slopes and forming a briefly glowing collar around the summit, it said.
Pyroclastic density currents (PDCs) — hazardous, high-speed mixtures of hot volcanic gas, ash, and rock fragments —descended the southeast and eastern upper slopes of Kanlaon within two kilometers of the crater, Phivolcs added.
The explosive onset generated a powerful shock wave recorded at a maximum of 218 Pascals by an infrasound station four kilometers away, manifesting as a loud booming sound heard within a 30-kilometer radius, it said.
Rumbling sounds were even reported as far as Southern Leyte, more than 175 kilometers east of the volcano, a phenomenon likely caused by the atmospheric refraction of explosion soundwaves, Phivolcs also reported.
Two minutes after the initial blast, the activity transitioned into 77 minutes of continuous and profuse ash emission on Thursday.
Driven by high wind speeds of approximately 12 meters per second at high elevations, the ash dispersed extensively over the Negros Island Region, with the heaviest accumulation recorded in the municipalities of La Castellana and Pontevedra, Phivolcs said.
The intense heat from the incandescent ballistics and superheated PDCs ignited two forest fires on the upper southern and southeastern margins of the volcano’s forest canopy, it added.
These grassfires burned throughout the night and were eventually observed to have died out by approximately 8:19 a.m. on Friday.
However, volcanic activity persisted as ash emissions resumed from 9:43 a.m. to 10:53 a.m. Friday, February 27, generating voluminous grayish plumes that rose 1,000 meters above the summit crater, Phivolcs said.
Phivolcs strongly recommend that communities within the 4-kilometer Permanent Danger Zone (PDZ) remain evacuated due to life-threatening hazards, including PDCs, ballistic projectiles, rockfalls, and volcanic gases.
Local government units were also advised to prepare communities within the six-kilometer radius for potential evacuation should unrest escalate and the Alert Level is raised from 2 to 3.
Affected residents are urged to safeguard themselves against the health impacts of ash inhalation and the resulting risks to transportation, food, and water resources, Phivolcs said.
Communities previously impacted by lahars must remain vigilant as intense rainfall could erode newly deposited ash and pyroclastic material on the upper slopes, potentially generating life-threatening lahars and sediment-laden streamflows, it added.
Civil aviation authorities have also been advised to warn pilots to avoid flying close to the volcano’s summit, as ash and ballistic fragments from sudden eruptions pose extreme hazards to aircraft, Phivolcs said.*
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