Report on Mayon (Philippines) — 10 January-16 January 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 January-16 January 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Mayon (Philippines). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 10 January-16 January 2018. 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 a phreatic eruption at Mayon was detected at 1621 on 13 January, generating an ash plume that rose 2.5 km and drifted SW. The seismic network recorded the event for 1 hour and 47 minutes. Trace amounts of ash fell in Barangays Anoling (4 km S), Sua (6 km SSW), Quirangay (6 km SSW), Tumpa (7 km SW), Ilawod (10 km SSW), and Salugan (9 km SSW) of Camalig, and in Barangays Tandarora (10 km SW), Maninila (18 km S), and Travesia (10 km SW) in Guinobatan. A sulfur odor was noted by residents of Camalig. Rumbling sounds were heard by residents in Anoling. The Alert Level was raised to 2 (on a 0-5 scale). Faint crater incandescence was first observed at 2216. A phreatic eruption began at 0849 on 14 January and lasted about five minutes, and another was detected at 1143 and lasted 15 minutes. Steam-and-ash plumes from both events rose from the crater but were mostly obscured by weather clouds. Anoling residents noted rumbling sounds and a sulfur odor, and minor amounts of ash fell in Camalig.
On 14 January PHIVOLCS raised the Alert Level to 3, noting a marked increase in activity characterized by three phreatic eruptions and 158 rockfall events between 1621 on 13 January and 1925 on 14 January. Bright crater incandescence was evident, signifying growth of a new lava dome and lava beginning to flow on the S flank. The report reminded residents to stay away from the 6-km-radius Permanent Danger Zone (PDZ) and the 7-km Extended Danger Zone (EDZ) on the S flank.
Three collapses of material occurred on 15 January, producing rockfall or small-volume pyroclastic density currents. They were detected by the seismic network at 0941, 1005, and 1107 and lasted five, seven, and eight minutes, respectively. The first two events appeared to have been from collapses of the lava-flow front and generated ash plumes that drifted SW and ashfall in multiple Barangays including Travesia, Muladbucad Grande (8 km W), Maninila, and Masarawag (5 km W) of the Guinobatan municipality, and several Barangays in the Camalig municipality. An ash plume from the third event rose about 1 km above the crater and drifted WSW.
During 15-16 January the new lava dome in the summit crater continued to effuse. Lava flows advanced 2 km down the Miisi drainage (S), and a small-volume flow was emplaced on the upper slopes of the Bonga drainage (SSE). The seismic network recorded multiple events including short-duration lava fountaining, 75 lava-collapse events corresponding to rockfalls along the front and margins of advancing lava, and short pyroclastic flows in the Miisi drainage. Ash plumes from collapse events in the summit crater produced ash plumes that rose 2 km and caused ashfall in Camalig, Guinobatan, and Polangui.
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.