The lava from the ongoing eruption of Mayon Volcano in Albay has moved further down the restive volcano, based on the bulletin issued by the Philippine Institute of Volcanology and Seismology (Phivolcs) on Tuesday, July 18. The approximate length of the lava flow along the Bonga gully on Mayon Volcano’s southeastern flank has advanced to about 2.4 kilometers, which is longer than the 1.4 km observed in the previous 24-hour monitoring. Phivolcs also observed lava flowing along the Basud gully on the eastern side, extending to a distance of 600 meters, while it remained at 2.8 km on the Mi-isi gully located on the southern side of Mayon. Meanwhile, the deposit of collapsed debris is still at 4 kilometers on the Basud Channel. “In the past 24-hour period, very slow effusion of lava from the summit crater of Mayon Volcano continued to feed lava flows and collapse debris on the Mi-isi and Bonga gullies, as well as rockfall and PDCs on these and the Basud gullies,” it pointed out.
(The Mayon Volcano ejects massive pyroclastic density currents (PDC) towards the Basud Gully in Sto. Domingo town in Albay province around 5:30 p.m. on July 10, 2023. (Niño Luces/Manila Bulletin)

Pulse tremors recorded anew

Phivolcs also noticed the re-occurrence of a “repetitive pulse tremor,” which started at 11 p.m. on July 16. There was a “varying interval and accompanying infrasonic signals detected with reported audible sounds,” it said. The Mayon Volcano Network also recorded 267 volcanic earthquakes, 150 rockfall occurrences, and three dome collapse-triggered pyroclastic density currents in the past 24 hours. According to Phivolcs, Mayon Volcano is still experiencing a relatively high level of unrest, and a potentially hazardous eruption is still possible within weeks or even days. It noted that Mayon remains on alert level 3 because of ongoing “increased magmatic unrest.” Phivolcs advised communities near the restive volcano to maintain increased vigilance against lahars and sediment-laden stream flows along channels draining the volcano edifice, as heavy rainfall could cause channel-confined lahars and sediment-laden stream flows. Since Mayon Volcano’s status was upgraded twice in the past month, first to level 2 on June 5 and then to level 3 on June 8, Phivolcs strongly advised that entry into the six-kilometer permanent danger zone be strictly prohibited. Furthermore, it warned that ash fall may occur in areas south of Mayon Volcano due to current wind patterns. Phivolcs advised pilots to avoid flying near the volcano’s summit because ash from a sudden eruption can be dangerous to aircraft.