PHIVOLCS reported that eruptive activity continued at Mayon during 27 June-4 July. Daily steam-and-gas emissions rose as high as 2.5 km above the crater and drifted multiple directions. Average daily measurements of sulfur dioxide emissions fluctuated between 595 and 1,002 tonnes per day. Slow lava effusion fed the growing dome and flows that advanced down the Mi-Isi (S) and Bonga (SE) drainages. Maximum lava flow lengths along the Mi-Isi drainage extended from 1.6 km on 28 June to 2.7 km by 2 July; the maximum in the Bonga drainage was 1.2 km during 27-28 June, reached 1.3 km on 29 June, and remained at that distance through 2 July. The dome remained unstable and produced incandescent rockfalls and pyroclastic density currents (PDCs, or pyroclastic flows) that sent material up to 4 km away from the crater; seismic stations recording 254-397 daily rockfall events and 4-17 daily PDC events (each lasting 2-4 min). An advisory report about increased activity on 30 June noted four dome-collapse PDC events between 1809 and 2000 that traveled 3-4 km down the Basud drainage, each lasted four minutes. Ashfall was reported during 29 June-1 July in Tabaco (about 13 km NW). The Disaster Response Operations Monitoring and Information Center (DROMIC) reported that as of 1800 on 3 July there were 18,717 people displaced from 26 barangays within the province of Albay, and overall 37,944 were affected. The Alert Level remained at 3 (on a 0-5 scale). Residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ), and 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 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)