Based on Phivolcs’ Mayon Volcano summary of 24-hour observation from 5 a.m. on Nov. 1 until 5 a.m. on Thursday, Nov. 2, a total of 187 volcanic earthquakes were recorded.

These activities include 179 volcanic tremors, each lasting from one to 12 minutes.

Phivolcs also recorded 175 rockfall events and four Pyroclastic Density Current (PDC) events.

From Oct. 31 to Nov. 1, Mayon had 113 volcanic earthquakes including 110 volcanic tremors that lasted one to 49 minutes long along with 133 rockfall events and three PDCs according to Phivolcs.

Slow effusion of lava flow

Monitoring of the Mayon Volcano Network also showed “slow effusion” of lava flow from the crater to lengths of 3.4 kilometers (km), 2.8 km, and 1.1 km along Bonga, Mi-isi, and Basud Gullies, respectively.

A lava collapse up to 4 km from the crater was also observed.

The monitoring also showed that the lava flows have “maintained their advances” to approximately 3.4 kilometers in Bonga (southeastern), 2.8 kilometers in Mi-isi (south), and 1.1 kilometers in Basud (eastern) Gullies.

Debris from rockfalls and PDCs resulting from the summit dome collapse remains within a 4-kilometer radius of the crater, Phivolcs said.

Meanwhile, it was noted that volcanic sulfur dioxide (SO2) emissions averaged 1,539 tonnes/day on Nov. 1.

Citing short-term observations from electronic tilt and GPS monitoring, Phivolcs noted an “inflation of the northwestern upper and middle slopes” since late July 2023 and October 2023, respectively.

“Longer-term ground deformation parameters from EDM, precise leveling, continuous GPS, and electronic tilt monitoring indicate that Mayon is still generally inflated relative to baseline levels,” Phivolcs said.

High level of unrest

In light of these developments, Phivolcs maintained Alert Level 3 for Mayon Volcano.

This status indicates that the volcano is currently at a relatively "high level of unrest" and a hazardous eruption within weeks or even days remains a possibility.

Phivolcs strongly recommended that the 6-km radius Permanent Danger Zone (PDZ) “remain evacuated” due to the danger of PDCs, lava flows, rockfalls, and other volcanic hazards.

Increased vigilance against PDCs, lahars, and sediment-laden streamflows along channels draining the edifice was also advised.

Moreover, Phivolcs noted that heavy rainfall could also “generate channel-confined lahars and sediment-laden streamflows in channels where PDC deposits were emplaced.”

In light of these conditions, Phivolcs strongly advises civil aviation authorities to instruct pilots to avoid flying near the volcano's summit, as ash from a sudden eruption could pose a threat to aircraft.

Phivolcs noted that based on the current prevailing wind pattern, ash fall events may “most likely occur” on the south side of Mayon.