By Chito Chavez
Mayon Volcano continued to exhibit sporadic and weak lava fountaining, continuous lava effusion and degassing from the summit crater on Thursday.
In a bulletin, the Philippine Institute of Volcanology and Seismology (Phivolcs) said 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 a.m., 7:56 a.m., 8:51 a.m., and 9:11 p.m.
The activity was accompanied by loud, booming sounds audible within 10 kilometers from the summit crater.
Phivolcs said 11 episodes of lava-collapse pyroclastic density current (PDC) events were visually observed between 8:51 a.m. on Thursday and 2:01 a.m. Friday.
The deposits made their way to Miisi, Basud and Bonga Gullies which were within two kilometers from the summit crater.
Throughout the night, quiet lava effusion fed lava flows and rockfall in the Miisi and Bonga-Buyuan channels and barrancos between them.
The Miisi and Bonga-Buyuan lava flows have advanced to 3.2 kilometers and 4 kilometers, respectively, from the summit crater.
Some 338 volcanic earthquakes, most of which corresponded to sporadic and weak fountaining events, two tremor events, 11 distinct episodes of PDC generation from lava collapse, and two 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.
Phivolcs said sulfur dioxide gas emission was measured at an average of 3,066 tons per day on February 1.
Electronic tilt and continuous GPS measurements indicated a sustained swelling or inflation of the edifice since November and October last year which is consistent with pressurization by magmatic intrusion.
Alert level 4 remains in effect over Mayon Volcano.
Phivolcs officials reminded the public to be vigilant and desist from entering the eight kilometer-radius danger zone and to be additionally vigilant against pyroclastic density currents, lahars and sediment-laden stream flows along channels draining the edifice.
State volcanologists called on civil aviation authorities to advise pilots to avoid flying close to the volcano’s summit as ash from any sudden eruption can be hazardous to aircraft.