PHIVOLCS reported that during 23-29 January there were 2-7 daily episodes of intense and sporadic lava fountaining at Mayon, each lasting 7-74 minutes. The lava fountains rose as high as 600 m above the crater rim, and fed flows in the Mi-isi and Bonga drainages and incandescent rockfalls on the summit area. Ash plumes rose 3-5 km above the crater. As many as three pyroclastic flows each day were detected by the seismic network, and had runout distances exceeding 5 km in the Buyuan drainage. Numerous rockfall events were generated by the growing and collapsing summit lava dome and traveled into the Bonga drainage, and from the front and margins of the advancing 3-km-long lava flow on the Mi-isi drainage. The Buyuan lava flow was 1 km long. Sulfur dioxide gas emissions were between 1,252 and 2,466 tonnes/day during 23-25 January. Heavy rain triggered lahars in the Binaan drainage during 28-29 January.

A cycle of energetic lava effusion with sporadic lava fountaining, and pyroclastic flows from lava-collapse events, occurred late on 29 January. The events were mostly visually obscured, and indicated by seismic data. The period began with a large-volume lava collapse at 1950 at the summit crater that generated pyroclastic flows in the Mi-isi and Bonga drainages. Lava fountaining was detected at 2016 and lasted eight minutes. This was followed by large-volume lava effusion that lasted 96 minutes, and was interspersed with sporadic lava fountaining and/or pyroclastic flows. Sporadic lava fountaining was visually and seismically detected until 2306, with lava fountains rising as high as 200 m. Ash plumes rose 1.5 km above the crater. Significant ashfall was reported in Camalig and Guinobatan, Albay before 2100, possibly resulting from the lava fountaining and pyroclastic flows.

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 periods of andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic density currents 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)