Phivolcs: Mayon unrest could turn explosive after record sulfur dioxide spike

MANILA, Philippines — Mayon Volcano remained under Alert Level 3 on Monday, July 13, after PHIVOLCS recorded its highest sulfur dioxide emission in 26 years over the weekend, warning that the volcano's ongoing eruption could still change and lead to explosive activity.

In a Saturday, July 11 advisory, state seismology bureau PHIVOLCS said Mayon emitted an average of 13,128 tonnes of sulfur dioxide per day, the highest level recorded at the volcano since 2000.

The latest 24-hour observation bulletin, dated July 13, showed sulfur dioxide flux at 5,842 tonnes per day based on July 12 measurements, lower than the weekend peak but still part of continuing unrest at the volcano.

PHIVOLCS also recorded lava effusion with lava flows along the Basud, Bonga and Mi-isi gullies, extending 3.8 kilometers, 3.2 kilometers and 2.1 kilometers, respectively.

The agency said Mayon also showed episodic minor Strombolian activity and short-lived lava fountaining. This refers to small to moderate volcanic bursts that eject glowing lava fragmets from the crater.

Mayon's seismic activity remained elevated, with 92 volcanic earthquakes and 299 rockfall signals recorded in the latest 24-hour observation period.

PHIVOLCS also observed fair crater glow visible to the naked eye, moderate plume emission drifting northeast and ground deformation marked by short-term deflation of the edifice with shorter-term inflation on the northeastern flank.

Possible explosive activity

PHIVOLCS earlier said the sharp rise in sulfur dioxide emissions could forewarn further eruptive activity at the summit crater and the continued generation of volcanic hazards around Mayon.

"DOST-PHIVOLCS would like to remind the public that Mayon Volcano is at Alert Level 3 but that there are currently new possibilities that the behavior of ongoing eruption could change and even lead to explosive eruption," the agency said in its July 11 advisory.

The agency warned that a potential explosive eruption could generate larger and longer pyroclastic density currents, or fast-moving mixtures of hot gas, ash and rock fragments, across all sectors of the volcano.

It also warned of ballistic projectiles, or rock fragments thrown out by sudden explosions, and heavier ashfall that may affect communities around Mayon.

PHIVOLCS said the impact of these hazards could be worsened by poor weather conditions over the volcano.

No entry into danger zone

PHIVOLCS reminded residents to stay out of the 6-kilometer permanent danger zone around Mayon.

It also warned against flying aircraft close to the volcano because ash and ballistic fragments from sudden eruptions may be hazardous.

Possible hazards under Alert Level 3 include rockfalls, landslides or avalanches, ballistic fragments, lava flows and lava fountaining, pyroclastic density currents, moderate-sized explosions and lahars during heavy and prolonged rainfall.

Local governments and residents were advised to prepare in case Mayon's activity escalates. — Renalyn Ramirez