A rapidly advancing cloud of superheated volcanic gas and debris swept down Mount Mayon early Tuesday, state volcanologists reported.

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) recorded a pyroclastic density current (PDC), locally called “uson,” plunging down the volcano’s southwestern flank along the Mi-isi Gully between 7:19 a.m. and 7:26 a.m. Volcanologists said the fast-moving surge was triggered by the collapse of an accumulating lava flow.

Despite the ongoing activity of Mayon Volcano, Volcano Monitoring and Eruption Prediction Division chief Ma. Antonia Bornas emphasized that the volcano remains under Alert Level 3, as overall monitoring parameters have not shown significant changes.

She noted that instead of advancing, the newest lava flow in the Mi-isi Gully began collapsing, leading to the disgorgement of lava and the generation of successive PDCs.

Meanwhile, PHIVOLCS Director Teresito Bacolcol echoed the need for vigilance, urging the public to remain calm but alert.

In addition to the pyroclastic flows, Mayon’s continued unrest is marked by persistent seismic and surface activity. According to the latest state bulletin, volcanologists recorded 336 rockfall events and 14 volcanic earthquakes—including five volcanic tremors lasting up to eight minutes—within a 24-hour observation period.

The volcano also continues its open-vent degassing, with sulfur dioxide emissions measured at 1,829 tonnes per day, while moderate plumes rising 1,000 meters above the crater and a visible crater glow persist at the summit.

As ash plumes blanketed municipalities such as Camalig and Guinobatan, reducing visibility to near zero, health and disaster agencies issued urgent safety guidelines.

The Department of Health advised residents to stay indoors, seal windows and doors with damp cloths, remain hydrated to ease throat irritation, and wear N95 masks when going outside to filter harmful abrasive particles.

PHIVOLCS strictly prohibits entry into the six-kilometer Permanent Danger Zone and warned civil aviation authorities to avoid flying close to the crater due to the risk of sudden ash hazards.