Activity at Mayon Volcano in the past 24-hour monitoring period was dominated by weak and shallow low-frequency volcanic earthquakes or LFVQs that are associated with discrete and rapid releases of volcanic gas from the summit crater. Some of these degassing events were accompanied by audible thunder-like sounds and entrained ash at the crater to produce “ashing” of short dark plumes. Between 5:33 PM 18 July and 04:34 AM 19 July 2023, a total of thirty (30) ashing events with durations of 20 to 40 seconds and plume heights of 150 to 300 meters, drifting southwest were recorded by seismic, infrasound, visual and thermal monitors. Slow effusion of lava from the summit crater of Mayon Volcano continued to feed and bulk up established lava flows on the Mi-isi (south), Bonga (southeastern) and Basud (eastern) gullies. Respectively, these lava flows have maintained distal lengths of approximately 2.8 kilometers, 2.4 kilometers and 600 meters from the crater. Rockfall and pyroclastic density currents or PDCs generated by collapses of the lava flow margins as well as of the summit dome deposited debris still within four (4) kilometers of the crater. In total, three hundred four (304) LFVQs, three (3) PDCs and one hundred thirty-seven (137) rockfall events were recorded by the Mayon Volcano Network. The combined seismic energy release of these, however, has not increased beyond the trend of effusive activity. Volcanic sulfur dioxide (SO2) emission averaged 1,945 tonnes/day yesterday, 18 July 2023. Short-term observations from electronic tilt and GPS monitoring indicate a deflation of the eastern lower flanks in early July 2023 and inflation of the northwest middle flanks in the third week of July 2023. 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.
Alert Level 3 is maintained over Mayon Volcano, which means that it is currently in a relatively high level of unrest and hazardous eruption within weeks or even days could still be possible. It is therefore 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 pyroclastic density currents, lahars, and sediment-laden streamflows along channels draining the edifice is also advised. Heavy rainfall could generate channel-confined lahars and sediment-laden streamflows in channels where PDC deposits were emplaced. Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden eruption can be hazardous to aircraft. Based on the current prevailing wind pattern, ash fall events may most likely occur on the south side of the volcano. DOST-PHIVOLCS maintains close monitoring of Mayon Volcano and any new development will be communicated to all concerned stakeholders.
DOST-PHIVOLCS