The effusive eruption of Mayon Volcano resulted in more rockfalls and lava dome collapses between Thursday, June 22, and Friday, June 23, data from the Philippine Institute of Volcanology and Seismology (Phivolcs) showed.

Phivolcs defines effusive or “quiet” eruption as the outpouring of lava onto the ground, as opposed to explosive eruption, which is characterized by violent magma fragmentation.

It recorded 339 rockfall events in Mayon Volcano in the last 24 hours, higher than the previous day’s record of 299 rockfall incidents.

Because of the “very slow” effusion of lava from the Mayon Volcano, the lava front occasionally collapses, causing rockfall events.

“Very slow effusion of lava from the summit crater of Mayon Volcano continued to feed lava flows and collapse debris on the Mi-isi (south) and Bonga (southeastern) gullies. The lava flows have advanced to maximum lengths of 2,500 meters and 1,800 meters along Mi-isi and Bonga gullies, respectively, from the summit crater while collapse debris have deposited to 3,300 meters from the crater,” Phivolcs said in a bulletin issued on Friday.

In addition, 13 dome-collapse pyroclastic density currents (PDCs) lasting one to four minutes were recorded, which is more than the eight PDCs from the day before.

Phivolcs describes PDCs as mixtures of fragmented volcanic particles or pyroclastics, hot gases, and ash that rush down the volcanic slopes or rapidly outward from a source vent at high speeds.

‘High-level’ unrest persists

Phivolcs said that Mayon’s current state could last for a few months and its alert level 3 status could be maintained.

Mayon Volcano has been on alert level 3 since June 8, indicating that a “hazardous eruption is possible within weeks or even days.”

It is “currently in a relatively high level of unrest as magma is at the crater,” Phivolcs pointed out.

The evacuation of residents within the six-kilometer permanent danger zone has been recommended due to the risk of PDCs, lava flows, rockfalls, and other volcanic hazards.

Phivolcs warned the public to be cautious of PDCs, lahars, and sediment-laden stream flows along channels draining the volcano edifice.

It pointed out that heavy rainfall could cause channel-confined lahars and sediment-laden stream flows on channels where PDC deposits were emplaced.

Likewise, it said that ash fall events may “most likely” occur on the south side of the volcano, based on the current wind pattern.

Phivolcs advised civil aviation authorities to ask pilots to avoid flying close to the volcano because ash from sudden eruption may pose hazards to aircraft.

Source:
courtesy of MANILA BULLETIN

by ELLALYN DE VERA-RUIZ

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