PHIVOLCS reported that the eruption at Mayon continued during 2-8 August, with slow lava effusion from the summit crater feeding flows on the S, SE, and E flanks. The length of the lava flow in the Mi-Isi (S) drainage remained at 2.8 km, the flow in the Basud (E) drainage remained at 600 m long, and the flow in the Bonga (SE) drainage was 3.4 km long. Collapses at the lava dome and from the lava flows produced incandescent rockfalls and pyroclastic density currents (PDCs, or pyroclastic flows) that descended the Mi-Isi, Bonga, and Basud drainages as far as 4 km. Each day seismic stations recorded 66-225 rockfall events, 1-9 PDC events, and 44-272 low-frequency volcanic earthquakes. Sulfur dioxide emissions were reported on most days, averaging between 969 and 3,465 tonnes per day, with the highest value recorded on 2 August. There was a total of 27 emissions of short, dark ash plumes (called “ashing” by PHIVOLCS) during 1-4 August. Daily seismicity during 3-8 August included 10-197 tremor events, each with durations of 1-18 minutes. A short-lived (35 seconds) ejection of lava at 0442 on 6 August was accompanied by seismic and infrasound signals. The Alert Level remained at 3 (on a 0-5 scale) and residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ). PHIVOLCS recommended that civil aviation authorities advise pilots to avoid flying close to the summit.

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)