Report on Mayon (Philippines) — 7 September-13 September 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 7 September-13 September 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Mayon (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 7 September-13 September 2016. Smithsonian Institution and US Geological Survey.
13.257°N, 123.685°E; summit elev. 2462 m
All times are local (unless otherwise noted)
On 8 September PHIVOLCS noted that recent changes at Mayon prompted a change in the Alert level from 0 to 1 (on a 0-5 scale). Continuous gas measurements consistently showed increased sulfur dioxide emissions above the baseline level of 500 tonnes/day, sometimes as high as 1,000 tonnes/day, since July. Global Positioning System data and tilt measurements showed a consistent inflationary trend since July, and precise leveling and electronic distance surveys the last week of August also indicated edifice inflation, possibly due to magma movement at depth. An earthquake swarm (146 events) located 10 km SE during 3-6 August likely indicated rock fracturing processes but may or may not be associated with magmatic activity. Steam emissions from the crater ranged from weak to moderate. PHIVOLCS reminded residents of the 6-km-radius Permanent Danger Zone (PDZ) around the volcano.
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.