Report on Mayon (Philippines) — 11 April-17 April 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 April-17 April 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, 11 April-17 April 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 the week ending on 8 April there had been a total of 116 low-frequency volcanic earthquakes, six high-frequency volcanic earthquakes, and three high-frequency short-duration harmonic tremors. The SO2 flux during the same period averaged 3,400 metric tons/day, which is still significantly above the baseline value of 500 tons/day. Deformation monitoring showed that the volcano was inflated, but the present trend revealed insignificant change. Moderate steaming was typical. During most of the week no glow was observed at the crater, except during 1915 to 2223 on 10 April when faint incandescence was observed at the crater using a telescope; the incandescence was graded as level 1 intensity. Alert Level 3 remained in effect, prohibiting entry within the 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.