PHIVOLCS reported that lava-dome extrusion at Mayon’s summit crater continued during 14-20 June, generating frequent lava flows and pyroclastic density currents (PDCs, or pyroclastic flows), and additional evacuations. Sulfur dioxide emissions ranged from 149-193 tonnes per day (t/d) during 13-14 June, rising to 826-1,004 t/d during 15-18 June (above normal baseline values of 500 t/d), and then dropping to 389 t/d on 19 June. The total number of rockfalls ranged from 265-309 events per day, resulting from partial collapses of the growing lava dome and lava flows. PDCs were recorded during 13-14 June (7), 14-15 June (3), 15-16 June (13), 16-17 June (9), 17-18 June (11), 18-19 June (5), and 19-20 June (2); each event lasted 2-6 minutes based on seismic signals. Lava flows remained active, with debris collapses throughout the week sending material into the Mi-Isi (S) and Bonga (SE) drainages. By 20 June lava flows reached 2.5 km down the Mi-Isi and 1.8 km down the Bonga drainages, and debris flows extended 3.3 km from the crater. Ashfall during 15-16 June was reported in the communities of Buga (36 km W), Nabonton (9 km W), Ligao (16 km W), Purok 7 (12 km S), and San Francisco (11 km SW). The Disaster Response Operations Monitoring and Information Center (DROMIC) reported that by 20 June there had been 38,975 people affected, 20,139 displaced, and 18,749 taking shelter in 28 evacuation centers across Albay. 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).

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.

Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Disaster Response Operations Monitoring and Information Center (DROMIC)