PHIVOLCS reported that since the Alert Level for Mayon was raised to 1 (on a 0-5 scale) on 21 August monitoring data had showed nothing notable. Changes in morphology of the dome and minor aseismic extrusion estimated at about 40,000 cubic meters was detected during 6 June-20 August based on daily visual and camera monitoring data. Based on these observations, the lava dome grew an additional 48,000 cubic meters by 4 October; re-mobilized light-colored ash had been deposited in Miisi Gully (S flank) beginning 2 October, likely derived from lava fragmentation during the extrusion process. Freshly extruded lava at the base of the summit lava dome was seen during an aerial survey conducted on 7 October. PHIVOLCS raised the Alert Level to 2 that same day. Daily white steam plumes were visible drifting down-flank and then to the W, WSW, and SSW during 8-10 October.

Electronic Distance Measuring (EDM), precise leveling, continuous GPS, and electronic tilt monitoring data showed that the volcano had been slightly inflated, especially on the NW and SE flanks, since 2020. Short-term inflation on the W to SW flanks and short-term deflation on the E and SE flanks had been detected since August.

Geological Summary. Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano of the Philippines. The steep upper slopes are capped by a small summit crater. Recorded eruptions since 1616 CE range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often damaged populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)