Report on Mayon (Philippines) — 30 December-5 January 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 30 December-5 January 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Mayon (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 30 December-5 January 2010. Smithsonian Institution and US Geological Survey.
13.257°N, 123.685°E; summit elev. 2462 m
All times are local (unless otherwise noted)
PHIVOLCS reported declining activity at Mayon from 28 December to 2 January. Steam plumes were emitted from the crater, but ash plumes were last seen on 29 December. In addition, the majority of the seismic signals originated from rockfalls and detached lava fragments rolling down the flanks from advancing lava flows. Sulfur dioxide emissions also decreased from close to 9,000 tonnes per day to about 2,600 tonnes per day. PHIVOLCS lowered the Alert Level from 4 to 3, and reminded the public that no human activity should occur within the 6-km radius Permanent Danger Zone (PDZ) around the volcano and the 7-km Extended Danger Zone (EDZ) on the SE flank. During 2-5 January, seismic activity indicated rockfall events related to the detachment of lava fragments at the upper slopes. Cloud cover at the summit prevented observations of steam plumes. Incandescence from the crater at night was noted.
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.