The minor explosive eruption at Mt. Kanlaon and rain that triggered river-confined lahar in two towns in Negros Occidental on Thursday afternoon is an indication that the volcano is moving closer to a major eruption, a Philippine Institute of Volcanology and Seismology (Phivolcs) official said on Friday, February 7.
It is moving closer to a major eruption since what occurred on Thursday was a minor explosive eruption, Ma. Antonia V. Bornas, Phivolcs Volcano Monitoring and Eruption Prediction Division chief, said.
“All paramaters, not just the event Thursday, are indicating Kanlaon is preparing for a major eruption”, she told DIGICAST NEGROS.
The minor explosive eruption at 3:11 p.m. Thursday lasted two minutes based on seismic and infrasound records of the Kanlaon Volcano Network, Phivolcs reported.
Phivolcs said because the eruption occurred during rainy weather, syn-eruption channel-confined lahars were immediately generated in the Buhangin River which flows through La Castellana and Moises Padilla, Negros Occidental.
Lahar flow was also reported in the Binalbagan River on Friday.
“Increased vigilance against potential syn-eruption lahars and sediment-laden stream flows in channels draining the edifice is strongly advised should intense rains occur during eruptive unrest,” Phivolcs said.
Syn-eruption lahars occur during or immediately after a volcanic eruption. They are also known as primary lahars.
The explosion also generated an airwave that was recorded at 70 Pascals five kilometers east of the summit crater and heard as a booming sound in Brgy. Yubo, La Carlota City, and Brgy. Sag-ang, La Castellana, Phiviolcs reported.
Thursday’s explosive eruption generated a poorly visible plume that rose 600 meters above the vent before drifting southwest, scattering thin ashfall over Sto. Mercedes and San Luis in Brgy. Sag-ang, Negros Occidental, it added.
Sulfurous fumes were also reported in several barangays of La Castellana.
Prior to the eruption on Thursday, SO2 flux at the volcano was measured at an average of 2,249 tons, a significant drop from the medium-term average of 4,484 tons since June 3, 2024, while degassing from the summit crater had been weak since the previous evening, Phivolcs said.
The upper to middle slopes of the Kanlaon edifice have been undergoing inflation or swelling since January 10.
Phivolcs said when occasional plugging of the volcanic conduit occur and SO2 emission and degassing weakens, the resulting pressure build-up within the conduit could trigger explosions such as Thursday’s event.
Alert Level 3 (magmatic unrest) prevails over Kanlaon Volcano.
This means that the magmatic eruption that occurred may be followed by similar short-lived explosive eruptions in the short term which may generate pyroclastic density currents (PDC) within the 6-kilometer radius area on the summit, Phivolcs said.
It recommended that communities within a 6-km radius of the summit be fully evacuated due to the danger of lava flows, rockfalls, pyroclastic density currents or PDCs and other related hazards, it said.
Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden eruption can be hazardous to aircraft, Phivolcs reiterated.
The Isabela Municipal Disaster Risk Reduction Management Office, in a Facebook post, informed residents near the Binalbagan River that there is an observed lahar flow and smell of sulfur in the river.
“It is advised them to wear face masks and prohibit fishing in the river,” it said.
Meanwhile, the Negros Occidental provincial government is still using its own funds to feed residents displaced by Kanlaon Volcano’s unrest in 15 evacuation centers in La Castellana, La Carlota City and Bago City, Gov. Eugenio Jose Lacson said.
They have not been able to use the P50 million provided by the Office of the President because it has not sent back the signed deed of donation needed for the use of the funds, Lacson said.*