Report on Mayon (Philippines) — 9 May-15 May 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 9 May-15 May 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Mayon (Philippines). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 9 May-15 May 2001. Smithsonian Institution and US Geological Survey.
13.257°N, 123.685°E; summit elev. 2462 m
All times are local (unless otherwise noted)
Volcanic activity increased at Mayon, with a lava dome collapse occurring on 13 May. On 12 May seismographs detected a series of explosions at Mayon's summit crater. The following day the SE-facing portion of the lava dome partially collapsed, leaving a V-shaped opening in the dome. The collapse produced small lava avalanches that reached a maximum runout distance of 300 m down the Bonga Gully. After the collapse, incandescence was observed at the dome and lava fragments fell into the gully. Seismic activity indicated frequent earthquakes, tremor, and explosions. On 14 May rockfalls dominated the seismicity. On 15 May there was a lull in activity, with no rockfalls or lava avalanches occurring. Alert Level 3 remained in effect, prohibiting entry within the 6-km-radius permanent danger zone. PHIVOLCS warned that lava flows and/or pyroclastic flows could be produced in the future and residents just outside of the permanent danger zone should be prepared to evacuate at any time.
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.