Report on Mayon (Philippines) — 18 July-24 July 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 July-24 July 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, 18 July-24 July 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 at Mayon was similar to the previous week. During 17-23 July seismicity consisted of four high-frequency and 37 low-frequency earthquakes, and 203 high-frequency short-duration harmonic tremors. An average of 4,100 metric tons per day of SO2 was emitted from the volcano, which was still above the baseline value of 500 metric tons per day. There was an overall deflationary trend and the intensity of incandescence observed at the crater ranged from barely visible to bright. Rockfalls occasionally rolled from the crater SE towards the Bonga Gully. The volcano remained at Alert Level 3 (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.