FILE PHOTO: Mayon Volcano at the Bonga gully is visible in this photo taken on Sept. 24 at Barangay Bonga in Legazpi City. —JOHN MICHAEL L. MANJARES/CONTRIBUTOR
Updated on December 8, 2023 at 9:51 a.m.
MANILA, Philippines — After almost six months, the alert level classification of Mayon Volcano has been lowered to alert level two, state volcanologists said on Friday.
In its advisory, the Philippine Institute of Volcanology and Seismology (Phivolcs) said it 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).”
Phivolcs lowered the alert classification after recording “a general decline in unrest since November.”
The decline was mostly evident in the volcano’s seismic activity as volcanic earthquakes have decreased from a monthly average of 11 events per day last month to nearly zero events per day in the first week of December.
It was also in contrast to hundreds of volcanic earthquakes recorded every 24 hours in the early days of Mayon Volcano’s alert level 3 classification.
Recorded rockfall and pyroclastic density currents (PDCs) also significantly decreased from monthly averages of 122 to 87 events a day and five to two events a day, respectively, between October and November to virtually zero events a day in the first week of December.
Volcanic sulfur dioxide (SO2) emission peaked at an average of 4,756 tonnes a day on August 16 and has since been decreasing and increasing “in cycles of generally lessened peaks.”
Monthly average SO2 emission increased from 1,173 to 1,417 tonnes a day between October and November before falling to an average of 1,095 tonnes/day in the first week of December.
However, the SO2 emission on Thursday only averaged 859 tonnes a day.
Phivolcs raised the classification of Mayon Volcano to alert level 3 last June.