8-minute Mayon explosion produced 5-km high volcanic ash column

State volcanologists on Tuesday said Monday afternoon’s eight-minute phreatomagmatic eruption generated a dense, five-kilometer tall column of volcanic ash, and was followed by two explosion-type earthquakes, several tremors and rockfall events throughout the day.

The eruption, which took place at 12:43 p.m., emitted a cloud of volcanic ash that covered the towns of Guinobatan, Camalig, Oas, Polangui, and Iriga City, according to the latest bulletin by the Philippine Institute of Volcanology and Seismology (PHIVOLCS).

Two explosion-type earthquakes, 15 tremor events, 35 rockfall events and two pyroclastic flows from lava collapse events were recorded by Mayon’s seismic monitoring network, said the bulletin.

Five instances of “intense but sporadic” lava fountaining that lasted between three to 30 minutes happened from 9:37 p.m. Monday to 5:25 a.m. Tuesday. The lava fountains from these episodes reached 500 to 700 meters high and produced ash plumes that went as high as 2.5 to three kilometers above the crater, said the bulletin.

Alert Level 4 remains in place over the restive volcano, which is one level away from the highest alert, which means a hazardous eruption is underway. The danger zone has been extended to eight kilometers from seven kilometers.

Monday’s eruption also generated pyroclastic density currents (PDCs) or flows on several gullies and rivers within four kilometers of the summit vent, and was followed by a minor degassing event at 5:51 p.m. that produced a 500 meter-high ash plume.

Lava flows at the Miisi and Buyuan gullies have advanced three kilometers and 200 meters from the summit crater, respectively. The volcano is emitting sulfur dioxide gas at an average rate of 992 tonnes per day -- but this was before the phreatomagmatic eruption, which sent residents who had returned home fleeing again.

Almost 36,000 people have fled to safety as of Tuesday morning, while the Mayon continues to spew lava and generate ash. Residents are advised to wear face masks, or damp cloth over their nose and mouth, and to stay indoors. —ALG, GMA News