MANILA — State seismologists on Friday lowered the alert level status of Mayon Volcano to 1 or “low level of unrest” as monitored parameters continue to decline.
The alert level status of Mayon was first lowered to 2 or moderate level of unrest last March 2018.
In its 9:30 AM bulletin, Phivolcs said “the likelihood of an eruption occurring within the immediate future has diminished.”
“However, the lowering of the alert status should not be interpreted that the volcano’s unrest has ceased, considering that eruptible magma has already accumulated beneath the edifice,” Phivolcs said.
State seismologists said the public is still reminded to avoid entry into the 6-kilometer permanent danger zone “due to perennial hazards of rockfall, avalanche, ash puff and sudden steam-driven or phreatic eruption at the summit area.”
“Furthermore, people living in valleys and active river channels are cautioned to remain vigilant against sediment-laden streamflows and lahars in the event of prolonged and heavy rainfall brought about by the advent of the rainy season,” Phivolcs said.
Phivolcs said the lowering of the alert level status is supported by the observations on volcanic earthquake activity, volcanic gas out put, visual observation of the summit and ground deformation.
For the past six months state seismologists recorded a daily average of one volcanic earthquake “typically attributed to rock fracturing beneath the edifice and occasional rockfall.”
“Rockfall events were likely initiated by intense rainfall or extreme winds over the volcano summit rather than lava extrusion. The overall low-level seismicity indicates that there is currently no active transport of eruptible magma to the shallow levels of the volcano,” it said.
The emission of sulfur dioxide from the volcano’s crater based on continuous gas spectrometry has stabilized between 300-700 tonnes per day since January, Phivolcs said.
It added that the latest flux was measured at 229 tonnes per day June 30, considerably below the baseline of 500 tonnes per day.
“The relatively low levels of SO2 flux indicate that passive degassing of stalled magma beneath the edifice has been transpiring,” Phivolcs said.
Based on its observation, steaming activity from the crater has ranged from weak to moderate.
The lava-dome presently occupying the crater has not exhibited significant changes in configuration this year, Phivolcs said.
“Crater glow or incandescence associated with superheated gas escaping the summit vent has been faint and only visible through the aid of a telescope,” Phivolcs said.
“The faint crater glow and stable lava dome are consistent with the presence of remnant magma from the 2018 eruption and the absence of magma re-supply to the shallow levels of the edifice,” it added.
Lastly, the ground deformation measurements on the volcano remain anomalous as the geodetic data from continuous Global Positioning Systems (GPS) and electronic tiltmeters and campaign Electronic Distance Meter (EDM) and Precise Leveling indicated a cycle of inflation or swelling of the edifice since the beginning of 2020.
“Moreover, inflation is slightly more prominent on the lower to middle slopes but is slight to negligible on the upper slopes, consistent with deep-seated magma that has yet to ascend the edifice,” state seismologists said.
“This agrees with the above observations of stable lava dome, faint crater glow and low gas emission since the beginning of 2020, all of which signify the cessation of magmatic activity,” it added.