Mayon Volcano in Albay province has been placed under Alert Level 3, indicating heightened volcanic unrest, following a moderately explosive eruption on Friday, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS).

The state volcanology agency raised the alert level from Alert Level 2 to Alert Level 3 in its 12:30 p.m. Mayon Volcano bulletin, issued after the eruption at 11:53 a.m. The eruption produced a “dense, rapidly rising and billowing ash plume” that reached 3,000 meters above the summit crater, PHIVOLCS said. Moderate winds dispersed the plume west-southwest, with ashfall expected in Daraga, Camalig, Guinobatan and nearby municipalities in Albay.

“This means that Mayon is in a new phase of magmatic eruption, with increased chances of lava flows and hazardous PDCs (pyroclastic density currents) or uson affecting the upper to middle slopes of the volcano in the immediate days to weeks,” PHIVOLCS said in the bulletin.

The bulletin's reference to a magmatic phase indicates that eruptive activity is now being driven by magma, a shift the agency tied directly to the elevated hazards. Pyroclastic density currents — fast-moving currents of hot gas and volcanic debris — and lava flows rank among the most dangerous volcanic phenomena, the kind of hazard that danger-zone evacuations are designed to guard against.

Under Alert Level 3, the agency recommended the evacuation of the six-kilometer permanent danger zone, citing hazards such as pyroclastic density currents, lava flows and rockfalls, among others. It also advised heightened vigilance against PDCs, lahars and sediment-laden streamflows along channels draining the volcanic edifice. Civil aviation authorities were likewise advised to instruct pilots to avoid flying close to Mayon Volcano — a routine precaution around erupting volcanoes, since drifting volcanic ash can damage aircraft engines.

Mayon, an active stratovolcano in the Bicol region of the Philippines, is one of the country's most active volcanoes and is renowned for its near-perfect conical shape. PHIVOLCS maintains a five-tier alert scale for the volcano, with Alert Level 5 denoting a hazardous eruption in progress — placing the current Alert Level 3 two steps below the maximum. Mayon's most destructive recorded eruption, in 1814, buried the town of Cagsawa, and its most recent major episode in early 2018 saw the alert raised to Alert Level 4, prompting the evacuation of tens of thousands of residents. Against that history, the bulletin's warning that lava flows and hazardous PDCs could affect the upper to middle slopes in the immediate days to weeks frames the period ahead as the critical window for monitoring the volcano.

— Edg Adrian A. Eva