Report on Mayon (Philippines) — 17 January-23 January 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 17 January-23 January 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, 17 January-23 January 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 activity increased at Mayon during the week and that all indicators suggested that the lava dome in the summit crater was becoming active although no new lava had reached the surface yet. During 17 and 18 January, 36 low-frequency-type volcanic earthquakes occurred over 24 hours, which scientists believed was caused by continued magma movement beneath the summit lava dome. During 19-23 January the number of recorded earthquakes increased to 60 events per day; tiltmeters continued to record inflation; and SO2 emission rates increased to 8,070 tons/day (a more than 4-fold increase from that seen in previous weeks). The Lignon Hill observatory reported that ash-entrained steam briefly erupted from the summit lava dome at 0932 on 22 January accompanied by a volcanic earthquake. The volcano remained at Alert Level 2.
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.