Sporadic and weak lava fountaining, continuous lava effusion and degassing from the summit crater characterized Mayon’s activity yesterday. Much of the activity produced low white to light-gray plumes, with the exception of four events that produced 750 to 1500 meter-tall gray ash plumes at 6:04 AM, 7:56 AM, 8:51 AM and 9:11 PM accompanied by loud booming sounds audible within 10 kilometers of the summit crater. Eleven (11) episodes of lava-collapse pyroclastic density current (PDC) events were visually observed between 8:51 AM yesterday and 2:01 AM this morning depositing along Miisi, Basud and Bonga Gullies within two kilometers of the summit crater. Throughout the night, quiet lava effusion fed lava flows and rockfall in the Miisi and Bonga-Buyuan channels and barrancos between these. The Miisi and Bonga-Buyuan lava flows have advanced to 3.2 kilometers and 4.0 kilometers, respectively, from the summit crater.
A total of three hundred thirty eight (338) volcanic earthquakes, most of which corresponded to sporadic and weak fountaining events, two (2) tremor events, eleven (11) distinct episodes of PDC generation from lava collapse and two (2) rockfall events were recorded by Mayon's seismic monitoring network. Rockfall events were generated by the collapsing lava front and margins of the advancing lava flows on the Bonga and Miisi Gullies. Sulfur dioxide gas emission was measured at an average of 3,066 tonnes/day on 01 February 2018. Electronic tilt and continuous GPS measurements indicate a sustained swelling or inflation of the edifice since November and October 2017, consistent with pressurization by magmatic intrusion.
Alert Level 4 remains in effect over Mayon Volcano. The public is strongly advised to be vigilant and desist from entering the eight (8) kilometer-radius danger zone, and to be additionally vigilant against pyroclastic density currents, lahars and sediment-laden stream flows along channels draining the edifice. Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden eruption can be hazardous to aircraft. DOST-PHIVOLCS maintains close monitoring of Mayon Volcano and any new development will be communicated to all concerned stakeholders.
