Report on Mayon (Philippines) — 12 July-18 July 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 July-18 July 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Mayon (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 12 July-18 July 2006. Smithsonian Institution and US Geological Survey.
13.257°N, 123.685°E; summit elev. 2462 m
All times are local (unless otherwise noted)
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.
Geologic Background. Beautifully symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the Philippines' most active volcano. The structurally simple edifice has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions date back to 1616 and 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 devastated populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.