Phreatic eruptions at Mayon on 13 July produced ash that fell up to approximately 5.3 km NE in Calbayog, Malilipot. The Alert Level was raised from 1 to 3 (scale is 0-5, 0 referring to No Alert status) after observers reported lava flows on the SE slopes, the predominant direction for lava flows and rockfalls. On 16 July, a danger zone 6 km from the summit was extended to 7 km in the SE area. Incandescent material was shed from an 800 m long lava flow moving SSE towards Bonga gully on 16 and 17 July. On 18 July, PHIVOLCS reported that the lava flow reached 1 km in length and incandescent boulders rolled 3 km towards the Bonga gully.

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), Associated Press, Manila Standard Today, Associated Press