THE Philippine Institute of Volcanology and Seismology (PHIVOLCS) on Friday lowered the alert level for Mayon Volcano in Albay, six months after it began spewing lava down its slopes.
PHIVOLCS said in a bulletin that it has ”recorded a general decline in unrest since November 2023.”
”DOST-PHIVOLCS is lowering the alert level of Mayon Volcano from Alert Level 3 (tendency towards a hazardous eruption) to Alert Level 2 (moderate level of unrest). However, the lowering of the alert status should not be interpreted to mean that the volcano’s unrest has ceased, considering that the edifice is still inflated and SO2 emissions remain high relative to baseline levels,” it said.
”The public is strongly advised to be vigilant and desist from entering the six-kilometer-radius Permanent Danger Zone (PDZ) to minimize risks from sudden explosions, rockfalls, and landslides.”
Explaining the basis for lowering the alert level, PHIVOLCS said volcanic earthquakes have decreased from a monthly average of 11 events per day in November 2023 to nearly 0 events per day in the first week of December 2023.
Rockfalls and pyroclastic density currents, or PDCs, also decreased from monthly averages of 122 to 87 events per day and 5 to 2 events per day, respectively, between October and November 2023, to virtually 0 events per day in the first week of December 2023.
”These decreases indicate that magma supply to the summit crater has significantly diminished, resulting in the cessation of lava effusion from the crater, lava collapse-driven rockfall, and PDC activity,” PHIVOLCS said.
The agency also noticed a ”stabilization and diminishing incandescence of lava deposits at the summit and depositional gullies” which are ”consistent with the cessation of magma supply to the summit crater.”
It said the pressurization of the Mayon edifice has abated in the past month, although the edifice remains generally pressurized (inflated) due to magma intrusion that has been transpiring since the onset of unrest in June 2023.
PHIVOLCS said the monthly average SO2 emission went up from 1,173 to 1,417 tonnes/day between October and November 2023 before falling to an average of 1,095 tonnes/day in the first week of December 2023.
SO2 emissions on December 7, 2023, averaged 859 tonnes/day.
”The overall weakening of cyclic SO2 emission indicates that volcanic gas from lava exposed on the crater and slopes of Mayon and from magma stored within the volcano is diminishing, but that minor volumes of magma are still periodically intruded in storage beneath the edifice, consistent with ground deformation and microgravity data,” PHIVOLCS said.
Thousands of people were evacuated due to Mayon’s unrest, prompting officials to place Albay province under a state of calamity to ensure the release of quick response funds to assist affected residents.
