Report on Mayon (Philippines) — 3 January-9 January 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 January-9 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, 3 January-9 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)
The Philippine Institute of Volcanology and Seismology (PHIVOLCS) stated in the 09 January Mayon Bulletin that major monitored parameters strongly suggest that activity is rapidly progressing beyond the usual background conditions at the volcano. Reports by the Ligñon Hill Observatory in Legazpi City disclosed that lava dome growth was occurring at the volcano's summit, with coinciding, slight ground tilt. In addition, voluminous volcanic gases were released from the summit crater, and there was a significant increase in earthquake occurrences for about a week that they believe is related to magma ascent. As of 9 January, near-continuous cloud cover prevented observations of the dome to determine if lava was present in the crater. Because reactivation of the volcano may eventually lead to the production of lava flows or pyroclastic flows, PHIVOLCS put the volcano at Alert Level 2 (increased and sustained volcanic unrest) and maintained 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.