Report on Mayon (Philippines) — 17 September-23 September 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 17 September-23 September 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Mayon (Philippines). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 17 September-23 September 2003. Smithsonian Institution and US Geological Survey.
13.257°N, 123.685°E; summit elev. 2462 m
All times are local (unless otherwise noted)
During 14 August to 18 September, seismicity at Mayon remained within background levels (less than five earthquakes/day). No volcanic earthquakes were recorded after 14 September. Moderate volcanic-gas emissions were observed during most of the report period. The sulfur-dioxide flux remained above baseline repose levels. Mayon remained at Alert Level 1 (on a scale of 0-5), with a 6-km-radius Permanent Danger Zone.
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.