Report on Mayon (Philippines) — 8 July-14 July 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 July-14 July 2009
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, 8 July-14 July 2009. 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 a "cone-shaped pile of hot, steaming old rocks," possibly from a previous eruption of Mayon, were seen during an overflight on 8 July and may be the source of recent summit incandescence. On 9 July, a leveling survey revealed that 1 cm of uplift previously measured during 15-22 June had been sustained. Incandescence at the summit crater had also intensified and was visible from the Lignon Hill Observatory (about 11 km SSE) without the aid of telescopes. Steam emissions were also noted. On 10 July, PHIVOLCS raised the Alert Level for Mayon from 1 (low level unrest) to 2 (moderate unrest) on a scale of 0-5.
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.