MANILA, Philippines – Less than a day after state volcanologists noted an increase in the number of volcanic earthquakes for Kanlaon Volcano in Negros Island, a moderately explosive eruption occurred early Tuesday, May 13.

The Philippine Institute of Volcanology and Seismology (Phivolcs) said the eruption began at 2:55 am on Tuesday and lasted 5 minutes.

It produced a “grayish voluminous plume” around 4.5 kilometers high. Ashfall hit the following areas in Negros Occidental:

La Carlota City – barangays of Cubay, San Miguel, Yubo, and Ara-al

Bago City – barangays of Ilijan and Binubuhan

La Castellana – barangays of Biak-na-Bato, Sag-ang, and Mansalanao

“Communities that experience ashfall must take all necessary precautions and use protective masks or wet cloth to prevent ash inhalation, with special attention given to vulnerable persons including the elderly, persons with respiratory or cardiovascular diseases, expecting mothers, and infants,” Phivolcs said.

Rumbling sounds were also heard in Barangay Pula, Canlaon City, Negros Oriental, and in La Castellana, Negros Occidental.

“Incandescent pyroclastic density currents or PDCs descended the southern slopes within approximately 2 kilometers of the crater,” Phivolcs added.

PDCs are “hazardous mixtures of hot volcanic gas, ash, and fragmented rock” that travel down volcanic slopes at high speeds.

“Large ballistic fragments were also observed to have been thrown around the crater within a few hundred meters and caused burning of vegetation near the volcano summit,” Phivolcs said.

Phivolcs earlier recorded 72 volcanic earthquakes at Kanlaon between 12 am and 12 pm of Monday, May 12 — election day.

The agency had also warned the public that a moderately explosive eruption could happen due to the blockage of volcanic gas and possible pressurization within the volcano. The blockage was evident as sulfur dioxide emission from Kanlaon averaged only 554 tons per day on Sunday, May 11.

Phivolcs maintained Alert Level 3 for Kanlaon, “which means that the volcano is in a state of magmatic unrest, with currently increased chances of short-lived moderately explosive eruptions that could generate life-threatening volcanic hazards.” These hazards include PDCs, ballistic projectiles, ashfall, and rockfall.

“Local government units must continue to prepare their communities within the PDC hazard zone for subsequent evacuation in case unrest further escalates and [a] hazardous worst-case explosive eruption becomes imminent,” the agency said.

Kanlaon has been under Alert Level 3 since December 9, 2024, when an explosive eruption also occurred.

Prior to Tuesday, its most recent eruption was last April 8 — characterized as a moderately explosive one, too.

Entry into the 6-kilometer-radius permanent danger zone around the volcano remains prohibited.

Kanlaon, which straddles the provinces of Negros Occidental and Negros Oriental, is one of the Philippines two dozen active volcanoes.