Despite Mayon Volcano's effusive eruption, there is no need yet to raise the volcano's alert status to level 4 according to Philippine Institute of Volcanology and Seismology (Phivolcs) OIC Director Teresito Bacolcol.
Mayon Volcano spews ash and lava as seen from Legaspi city, Albay, on June 11, 2023. The province of Albay was placed under a state of calamity due to the threat of an eruption of Mayon Volcano. The office of Civil Defense had evacuated 2,638 families in the towns of Camalig, Ligao City, Daraga, Guinobatan, Malilipot and Tabaco City. (Ali Vicoy)
During a public briefing on Monday, June 12, Bacolcol explained that while the volcano had an effusive eruption, the alert level cannot be raised yet since they are looking at parameters before deciding to do so.
"Yung effusive eruption involves slow release of magma onto the edifice of the volcano. Usually yung lava coming from an effusive eruption medyo low in dust. The lava flows are typically slow-moving and can be observed as rivers of molten rock," he said.
In its latest Mayon Volcano bulletin, Phivolcs said that as of 7:47 p.m. on June 11, lava flow activity has commenced from the summit crater of the volcano.
It added that this development was accompanied by only weak seismic activity and a slight swelling of the upper portions of the edifice prior to lava flow based on electronic tilt data.
To raise it to alert level 4, Bacolcol stated the specific parameters they are checking constantly such as the sudden decrease of sulfur dioxide gas and an increase in seismic activity.
"So if there is a sudden decrease of sulfure dioxide, ibig sabihin natrap yung gas doon sa loob ng lava dome and if there's a sudden release of sulfur dioxide then it could result to explosive eruption," he explained.
In the bulletin Phivolcs released, it said that they have recorded 21 weak volcanic earthquakes and 260 rockfall events. While it increased, Bacolcol stated that these are not strong and the seismic energy that was released was only at the background level.
Bacolcol also added that they are monitoring if there will be an inflation at the volcanic edifice, but so far they have only seen an inflation at the upper part or upper slope.
Lastly, he said they are also on the lookout for an increase in the mass flux which means the lava flows are getting longer, an increase in pyroclastic density currents (PDC) events, and the presence of lava fountaining. They are also monitoring if there will be minor explosions.
"Effusive eruptions are generally less violent than explosive eruptions and it could produce less ash. Hopefully ganito lang yung magiging situation hindi na ito mageevolve pa into an explosive eruption," Bacolcol stated.