LEGAZPI CITY — The Philippine Institute of Volcanology and Seismology (Phivolcs) on Tuesday lowered the alert status of Mt. Mayon to Level 3 but warned the public that the volcano remains restive.
A Phivolcs advisory issued Tuesday said the lowering of the alert status from Level 4 (which means hazardous eruption is imminent) to Level 3 (decreased tendency towards hazardous eruption) was due to the continued decline in the volcano’s activities, based on the monitored parameters, such as volcanic quakes, magma build-up, gas emission, crater glows, lava flows, and ground deformation.
Phivolcs resident volcanologist here, Dr. Ed Laguerta, explained in a press conference Monday that Mayon’s activity has declined, as shown by reduced intensity and frequency of events, suggesting a gradual depletion of eruptible magma at the shallow levels of the edifice.
Activity has diminished to sporadic degassing with associated ash plumes, weak lava fountaining, quiet lava flow, and lava collapse, interspersed with two to four days of relative quiescence.
Laguerta said there were low frequency events associated with degassing at the summit and signals of rockfall and small volume of pryoclastic density currents generated by the collapsing front and margins of lava flows on the Miisi, Bonga and Basud gullies.
In the past 24 hours, a total of only four volcanic earthquakes and 44 rockfall events were recorded by the seismic monitoring network, he said.
In terms of ground deformation, data from Precise Leveling (PL) surveys and real-time electronic tilt continued to record deflation of the lower slopes that began on Feb. 20, but based on medium-term PL data, the volcano is still inflated.
Laguerta said in terms of gas emission, the sulfur dioxide (SO2) emission flux throughout the eruption had varied from a maximum of 4,270 tons/day to 1,400 tons/day on March 3. These concentrations are significantly lower than those measured in past eruptions and are consistent with batches of partially degassed magma that has incrementally risen to shallow depths within the edifice. SO2 emission was measured on Monday at an average of 2,560 tons/day.
Laguerta said the lowering of Mayon’s alert status from Level 4 to Level 3 indicates that there is decreased tendency towards explosive eruption but should not be interpreted that unrest has ceased.
He added that the volcano can be expected to continue generating volcanic earthquakes, magmatic gas output and weak surface processes, such as sporadic degassing and lava effusion events, steam-driven explosions, rockfall and pryoclastic density currents.
He, however, said that in the event of uptrend or pronounced change in the monitoring parameters, the alert status may be raised again to Level 4.
On the other hand, if there is a noticeable and persistent downtrend in the monitoring parameters, then the alert status may further be lowered to Alert Level 2.
The public is still warned to avoid entering the 6-km. permanent danger zone due to perennial hazards of rockfall, avalanche, ash puff and sudden steam-driven or phreatic eruption at the summit area.
In view of the lowering of Mayon Volcano’s alert status, Albay Governor Al Francis Bichara issued an advisory for the full decampment of evacuees living inside the 8-km. and 7-km. radius buffer zone, while the remaining evacuees inside the 6-km. radius of the volcano shall remain in the evacuation centers.
In a report released Tuesday by the Albay Public Safety Emergency Management Office, there are 2,666 families or 10,836 individuals who will remain in evacuation centers.
Affected by Mayon Volcano’s eruptive activities are Tabaco City with 569 families or 2,214 individuals as evacuees, and the municipalities of Daraga (337 families or 1,552 individuals); Camalig (378 families or 1,693 individuals); Malilipot (1,303 families or 5,067 individuals); and Guinobatan (79 families or 310 individuals).
The municipalities of Bacacay and Sto. Domingo, and cities of Legazpi City and Ligao will have a full decampment. (Connie Calipay/PNA)
