Report on Mayon (Philippines) — 6 June-12 June 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 6 June-12 June 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, 6 June-12 June 2001. Smithsonian Institution and US Geological Survey.
13.257°N, 123.685°E; summit elev. 2462 m
All times are local (unless otherwise noted)
Rockfalls, small avalanches, moderate steam emission, and fair-to-bright crater glow dominated the visible volcanic activity at Mayon during the week. Partial lava-dome collapses occurred on 11 June at 1347 and on 12 June at 1819. The 11 June collapse produced a small pyroclastic flow that descended the Bonga Gully, reaching an elevation of 1,480 m and producing a thin ash cloud that drifted to the E. The 12 June collapse sparked a period of vigorous, continuous emission of lava fragments for ~1 hour. During the week up to 198 rockfall events were detected per day. A maximum of 2,700 metric tons of SO2 was measured per day, which was lower than the previous week but above the baseline value of 500 tons/day. Alert Level 3 remained in effect, prohibiting entry within the 6-km-radius permanent danger zone. PHIVOLC warned that residents around the volcano, especially those staying in areas facing the Bonga Gully and the SE sector, should be vigilant and prepared to evacuate at any time.
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.