MANILA, Philippines – A “moderately explosive eruption” at Kanlaon Volcano in Negros Island on Monday evening, June 3, prompted state volcanologists to place the volcano under Alert Level 2.

In a bulletin issued at 8 pm on Monday, the Philippine Institute of Volcanology and Seismology (Phivolcs) said the eruption occurred at 6:51 pm on Monday and lasted 6 minutes.

It “produced a voluminous and incandescent plume that rapidly rose to 5,000 meters” or 5 kilometers.

There were also “pyroclastic density currents or PDCs approximately 2 to 3 kilometers down the southern and southeastern slopes” of Kanlaon. PDCs are made up of fragmented volcanic particles, gases, and ash that travel down volcanic slopes at high speeds.

Phivolcs observed a “relatively strong” volcano-tectonic (VT) earthquake before the eruption as well. It was a magnitude 3.5 quake which occurred “some 2 kilometers north of the summit crater” at 6:47 pm, and had a depth of around 10 kilometers, the agency added in a separate report released on Tuesday, June 4.

The upgrade to Alert Level 2 means there is “increasing unrest” which is “driven by shallow magmatic processes.” Eventually, there may be “further explosive eruptions” or even a “hazardous magmatic eruption,” warned state volcanologists.

Several communities already reported “coarse ashfall and sulfurous odors” on Monday evening. Phivolcs advised affected residents to “cover their nose and mouth with a damp, clean cloth or dust mask.”

Permanent danger zone

There is also a 4-kilometer-radius permanent danger zone (PDZ) surrounding the volcano, which should be off-limits.

Phivolcs said barangays with areas within Kanlaon’s PDZ are:

• Ara-al and Yubo in La Carlota City, Negros Occidental
• Sag-ang, Mansalanao, Cabagnaan, and Biaknabato in La Castellana, Negros Occidental
• Minoyan in Murcia, Negros Occidental
• Codcod in San Carlos City, Negros Occidental
• Masulog, Pula, and Lumapao in Canlaon City, Negros Oriental

“Local government units, disaster officials, and the general public are urged to heed avoidance of the PDZ, as the chances of similar explosive eruptions occurring are significant, thus increasing the threat of volcanic hazards such as PDCs and ballistic projectiles within the PDZ,” the agency said.

In Canlaon City, Mayor Jose Chubasco Cardenas immediately ordered evacuation for residents of four barangays: Masulog, Malaiba, Lumapao, and Pula.

Phivolcs also advised aircraft not to fly close to the volcano’s summit “as sudden explosions can generate ash and rock fragments” that may be damaging.

History, outlook

Kanlaon, one of the Philippines’ two dozen active volcanoes, “occasionally exhibits phreatic and short-lived explosive eruptions that produce small-magnitude hazards,” according to Phivolcs. Phreatic means the eruption is steam-driven.

“Of the 43 eruptions recorded since 1866 including this most recent one, only the 1902 eruption was magmatic and associated with the generation of small-volume lava flows on the upper slopes,” added the agency.

Before Monday, Kanlaon’s last eruption was recorded nearly six and a half years ago on December 20, 2017. At the time, the volcano was under Alert Level 2 on a scale of 0 (normal) to 5 (hazardous eruption in progress).

Also prior to Monday’s eruption, Kanlaon had been under Alert Level 1 since March 11, 2020. But Phivolcs noted that the volcano “has been exhibiting periodic swarms of VT earthquakes since Alert Level 1 was raised.”

“Since 2023 alone, five advisories on increased seismic activity have been released, the latest of which was last [May 26],” the agency said.

Sulfur dioxide has also averaged around 1,273 tons per day in 2024, which is “substantially above the background emission of less than 300 tons per day.”

Kanlaon’s current unrest may lead to one of these three scenarios, according to Phivolcs:

• “If monitoring parameters are sustained, phreatic and short-lived explosive eruptions may subsequently occur and produce small-magnitude hazards that will endanger areas” within the PDZ. “Alert Level 2 will be maintained until such time that monitoring parameters significantly change.”

• “If seismic, ground deformation, and volcanic gas parameters worsen, magmatic eruption may become likely…. Eruptive activity could generate volcanic hazards that will endanger areas within the lava flow and PDC hazard zones…. Alert Level 3 will be raised.”

• “If monitoring parameters decline, unrest is driven by very shallow hydrothermal processes. Alert level will step down to Alert Level 1 after sufficient observation has elapsed.”

Kanlaon is currently the only volcano under Alert Level 2. Mayon in Albay, Bulusan in Sorsogon, and Taal in Batangas are all under Alert Level 1. – Rappler.com