Mayon Volcano’s current state is “largely similar” to its 2014 eruption based on the parameters observed over the previous week, said the Philippine Institute of Volcanology and Seismology (Phivolcs).
“Low-rate effusive eruption of degassed lava has been transpiring for the past week accompanied only by slight increases in volcanic SO2 (sulfur dioxide) emission, seismic and ground deformation parameters,” Phivolcs said in its volcanic activity report released on Sunday night, June 18.
“The very low mass eruption rate generates sluggish lava flows and intermittent collapse of the summit lava dome and lava flow margins that feed frequent rockfall and occasional small-volume PDCs (pyroclastic density currents) within the permanent danger zone,” Phivolcs said.
Science and Technology Secretary Renato Solidum told the Manila Bulletin in a text message on June 16 that the ongoing eruption at Mayon Volcano is a “non-explosive eruption characterized by gentle release of lava from the crater.”
Given the similarities to the 2014 eruption, Phivolcs said that Mayon’s current state may persist for a few months.
Mayon Volcano’s alert level 3 status may also be maintained.
The Philippine Institute of Volcanology and Seismology (Phivolcs) said a very slow lava effusion from Mayon Volcano’s summit crater continued for the fifth night on June 15, 2023, resulting in more rockfall events and pyroclastic density currents. (ALI VICOY/MANILA BULLETIN)
3 possible scenarios
Despite the similarities between Mayon Volcano’s 2014 eruption and the current unrest, Phivolcs is not discounting three eruption scenarios, similar to the 2006, 2018, and 2000 events, if changes in monitored parameters occur.
In the first scenario, Phivolcs said that if apparent rates of extrusion increase, SO2 emission increases, seismic activity persists, and a cycle of inflation and deflation of the edifice occurs, a slow and sustained lava extrusion similar to the 2006 eruption may occur.
These activities could last for several months, and the alert level will be raised to 4.
In the second scenario, lava fountaining and lava flow with occasional explosions and PDCs within the six-kilometer permanent danger zone, similar to the 2018 eruption, may occur if SO2 emissions increase significantly, seismic activity increases, and inflation of the entire edifice occurs, Phivolcs said.
The second scenario suggests that these activities could continue for a few months. The alert level may also be raised to 4.
In the third scenario, an explosive eruption with high-intensity lava fountaining, long lava flows, and PDCs on all sectors that could exceed the six-kilometer permanent danger zone, similar to the 2000 eruption, may occur if SO2 rapidly escalates or drops, and volcanic earthquake activity and ground deformation occur.
Phivolcs said these activities in the third scenario may last several days to weeks, and the alert level will be raised to 5.
Sustained lava flow, pyroclastic density currents, rockfall events
The “very slow” effusion of lava from the Mayon Volcano’s summit crater continued to feed lava flows and cause debris to collapse on the Mi-isi and Bonga gullies on the south and southeast sides in the past 24 hours, according to Phivolcs’ volcano bulletin issued at 8 a.m. on Monday, June 19.
“The lava flows have advanced to maximum lengths of 1,500 meters from the summit crater while collapse debris have deposited to 3,300 meters from the crater,” it said.
Five dome-collapse pyroclastic density currents that lasted three minutes and 265 rockfall events were also recorded by the Mayon Volcano Network.
“Continuous moderate degassing from the summit crater produced steam-laden plumes that rose 600 meters before drifting to the general west,” it added.
Alert level 3 stays
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.
