Report on Mayon (Philippines) — 6 January-12 January 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 January-12 January 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on Mayon (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 January-12 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 that steam emissions were seen rising from Mayon's crater from 5 to 12 January during periods of clearer weather; meteorological clouds often prevented observations of the summit. Weak incandescence from the crater was occasionally seen at night. The majority of the seismic signals originated from rockfalls and detached lava fragments rolling down the flanks. Sulfur dioxide emissions fluctuated between 670 and 1,900 tonnes per day. On 12 January, PHIVOLCS noted that ground deformation measurements showed a deflationary trend compared to a 2 December 2009 survey. These measurements, along with decreased seismicity and sulfur dioxide output, prompted PHIVOLCS to lower the Alert Level to 2 on 13 January.
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.