Report on Mayon (Philippines) — October 2009
Bulletin of the Global Volcanism Network, vol. 34, no. 10 (October 2009)
Managing Editor: Richard Wunderman.
Mayon (Philippines) Increased activity in mid-2009; November 2009 eruption
Please cite this report as:
Global Volcanism Program, 2009. Report on Mayon (Philippines). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 34:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200910-273030.
13.257°N, 123.685°E; summit elev. 2462 m
All times are local (unless otherwise noted)
On 10 August 2008 an explosion and resulting ash plume followed weeks of increased activity and summit incandescence (BGVN 34:02). According to a Philippine Information Agency (PIA) Daily News Reader press release, the 10 August eruption was followed by an M 5.8 earthquake on 15 August and a series of aftershocks that continued through at least 20 August.
On 10 July 2009, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) noted increased activity beginning in June 2009. According to PHIVOLCS, there was a rise in low-frequency volcanic earthquakes, a ground uplift of ~ 1 cm, moderate steam emissions, and summit incandescence. An 8 July overflight discovered the crater contained a "cone-shaped pile of hot, steaming old rocks." The fresh deposits were possibly from a previous eruption, and may have been the source of the glow in the crater. The Alert Level for Mayon was raised from 1 (low level unrest) to 2 (unrest which could lead to more ash explosions or eventually to hazardous magmatic eruptions).
According to a 6 August 2009 article from the Philippine Daily Inquirer, resident PHIVOLCS volcanologist Eduardo Laguerta reported that the number of earthquakes at Mayon had decreased by early August 2009. However, the Inquirer reported that SO2 emissions had increased, with a maximum of 1,977 tons per day on 6 August, compared to 500 tons per day when there is no activity.
PHIVOLCS reported that 11 earthquakes were detected during 14-15 September, with steam plumes drifting NW and ENE. On 15 September, three ash explosions produced a brownish ash plume that rose 700 m above the crater and drifted SW. On 28 October a minor explosion produced a brownish ash plume that rose 600 m above the crater and drifted NE, preceded by 13 volcanic earthquakes over the previous 24-hour period.
On 11 November 2009 another ash eruption occurred at 0158 that lasted for ~ 3 minutes and ejected incandescent rock fragments seen from nearby villages. The explosion was accompanied by rumbling sounds and light ashfall in surrounding areas to the SW, W, and NW. According to the Inquirer, a second explosion was recorded at 0702, with an ash plume reaching 300 m above the crater. The Inquirer reported that residents in Daraga township to the S were ordered to evacuate early, but that further mass evacuations would not be ordered until the Alert Level was raised to Level 3. An aviation ash advisory from the Tokyo VAAC noted continuous ash erupting in MTSAT-IR satellite imagery at 0800 on 11 November.
A 21 November 2009 article from Vox Bikol confirmed that as of 17 November, Mayon continued to exhibit summit incandescence and emit fluctuating amounts of SO2. Due to the continuing unrest PHIVOLCS installed additional seismic monitoring equipment, including three sets of broadband instruments from the Japan International Cooperating Agency (JICA).
A news article from Vox Bikol stated that PHIVOLCS did not observe summit incandescence during 2-3 December due to heavy cloud cover, but as of 4 December 2009 ground deformation and moderate steam emissions were continuing. PHIVOLCS continued to enforce the 6-km-radius Permanent Danger Zone (PDZ) and the 7-km-radius Extended Danger Zone (EDZ) on the SE flank, and urged residents to avoid river channels that are prone to lahars.
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.
Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); Philippine Daily Inquirer (URL: http://www.inquirer.net/); Tokyo Volcanic Ash Advisory Center (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Vox Bikol (URL: http://www.voxbikol.com/); Philippine Information Agency (URL: http://www.pia.gov.ph/).