Report on Mayon (Philippines) — 14 March-20 March 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 14 March-20 March 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, 14 March-20 March 2001. 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 during 15 to 19 March, 10-37 low-frequency earthquakes were recorded daily. An average of 2,900 metric tons per day (t/d) of SO2 was recorded during the previous week, which was significantly above the baseline value of 500 t/d. Many days a slight inflationary trend was detected at the volcano's edifice and moderate steaming was seen. No incandescence was observed at the crater. PHIVOLCS warned that instrumental and visual observations suggested that an eruption may occur in the coming weeks and that the volcano remained at Alert Level 3. Observations revealed that the lava dome growing at the summit had overlapped the pre-existing SE rim of the summit crater. Further growth of the lava dome towards the SE could result in rockfalls and avalanches that would be channeled down the SE-flank Bonga Gully. In addition, large pyroclastic flows could occur down the volcano's SE slope.
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.