The Philippine Institute of Volcanology and Seismology (Phivolcs) observed a renewed eruptive activity at the Mayon Volcano’s summit crater, characterized by intermittent “ashing” and increased lava effusion on Monday, July 31.
“Beginning at approximately 6 p.m. on July 31, eruptive activity at Mayon became dominated by phases of intermittent ashing alongside increases in the apparent rates of lava effusion from the summit crater,” Phivolcs said in its 8 a.m. bulletin on Tuesday, Aug. 1.
It noted that the ashing phases ranged in length from one to 43 minutes and were consisted of one to 16 discrete low-frequency volcanic earthquakes (LFVQs) that lasted between 30 seconds and one minute and 17 seconds.
Phivolcs said 100-meter gray ash plumes were produced and drifted northeastward.
On July 31, 2023, the lava effusion from the summit crater of the Mayon Volcano continued for the eighth consecutive week, feeding rockfall and lava flows in the Mi-isi, Bonga, and Basud gullies. (Screengrab from Phivolcs / Facebook)
‘Rapid’ lava effusion
“Shortly after ashing commenced, new lava began effusing rapidly from the crater and fed the established lava flows on the Bonga (southeastern), Mi-isi (south), and Basud (eastern) gullies as welll as frequent rockfall downslope,” Phivolcs.
The lava flows in the gullies of Bonga, Mi-isi, and Basud have advanced by 2.8 kilometers, 3.4 kilometers, and 600 meters respectively, from the crater.
Phivolcs recorded 258 volcanic earthquakes, including one tremor event that lasted one minute and 30 seconds, and 256 LFVQs triggered by 57 ashing events, and 100 rockfall events in the past 24 hours.
Alert Level 3
The Mayon Volcano is still on Alert Level 3, which means that a hazardous eruption is still possible within weeks or even days.
Communities near the restive volcano are recommended 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.