PHIVOLCS reported that the eruption at Mayon continued during 16-22 August, with slow lava effusion from the summit crater feeding flows on the S, SE, and E flanks. The lengths of the lava flow in the Mi-Isi (S), Bonga (SE), and Basud (E) drainages remained at 2.8 km, 3.4 km, and 1.1 km, respectively. Collapses at the lava dome and from the lava flows produced incandescent rockfalls and pyroclastic density currents (PDCs, or pyroclastic flows) that descended the three drainages as far as 4 km. Each day seismic stations recorded 60-154 rockfall events and 1-7 PDC events, though no PDC events were recorded during 21-22 August. There were 23-175 volcanic earthquakes, including 4-96 tremor events, each with durations of 1-80 minutes. Sulfur dioxide emissions averaged between 753 and 4,756 tonnes per day, with the highest value recorded on 16 August. 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)