Report on Mayon (Philippines) — 17 January-23 January 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 17 January-23 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, 17 January-23 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 during 16-17 January Mayon’s seismic network recorded 143 lava collapse events associated with rockfalls along the front and margins of advancing lava and pyroclastic flows in the Miisi (S), Matanag (SE), and Buyuan (SE) drainages. These events generated ash plumes that drifted SW. During 17-20 January effusion of lava at the summit and collapse events continued. Two pyroclastic flows traveled around 3 km down the Miisi drainage. Rockfall events were generated by the collapsing lava front and margins of the advancing 3-km-long lava flow in the Miisi drainage, and from the summit into the Matanag, Buyuan, and Bonga (SE) drainages. Ash plumes continued to drift SW. Sulfur dioxide gas emissions were 1,478 tonnes/day on 18 January and 1,131 tonnes/day on 19 January. During 20-21 January there were 14 rockfall events and 10 pyroclastic flows recorded by the seismic network.
During 21-22 January there were 64 rockfall events and one pyroclastic flow recorded. Strombolian activity generated lava fountains 500 and 200 m high at 1045 on 21 January and at 0225 on 22 January, respectively. Ash plumes rose 1.3 km high and drifted SW, causing ashfall in Oas and Guinobatan (12 km SW). Lava flowed more voluminously, adding to the advancing Miisi lava flow (over 3 km long) and feeding two new lava flows on the Bonga and upper Buyuan drainages.
At 1243 on 22 January an eight-minute-long phreatomagmatic event generated a dense, 5-km-high ash plume that drifted W. Ashfall was reported in the municipalities of Guinobatan, Camalig (11 km SSW), Oas, Polangui (20 km WNW), and Iriga City (34 km NW). The event also generated pyroclastic flows that traveled as far as 4 km down multiple drainages including Miisi, Bonga, Buyuan, Basud, San Andres, Buang, Anoling. PHIVOLCS raised the Alert Level to 4 (on a 0-5 scale) and extend the Danger Zone to an 8-km radius. A minor event at 1725 produced a 500-m-high ash plume. Between 2137 on 22 January and 0525 on 23 January there were five episodes of intense and sporadic lava fountaining, each lasting 3-30 minutes. The lava fountains rose 500-700 m high, and generated ash plumes that rose 2.5-3 km above the crater. The events fed lava flows on the Miisi and Bonga drainages, sprayed near-vent lava spatter, and fed incandescent rockfalls around the summit area. The Buyuan lava flow was 200 m long. According to news articles posted on 23 January about 40,000 people have been evacuated, and airports in the cities of Legazpi City (13 km SSE) and Naga (66 km NW), and on the nearby island of Masbate (100 km S) were closed.
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.