Report on Mayon (Philippines) — 1 August-7 August 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 August-7 August 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, 1 August-7 August 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 during 1-4 August at Mayon consisted of high SO2 emission, high- and low-frequency harmonic tremor and low-frequency volcanic earthquakes, slight inflation of the edifice, and the ejection of lava fragments up to 100 m above the crater rim. PHIVOLCS stated that activity had decreased since the 26 July eruptions and the volcano was in a mild state of eruption. According to news reports, approximately 26,500 people were still evacuated from their homes near the volcano. Mayon remained at Alert level 5, the highest level.
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.