This serves as a notice for the lowering of the alert status of Mayon from Alert Level 2 (moderate level of unrest) to Alert Level 1 (low level of unrest).
Since the lowering of alert status from Alert Level 3 to Alert Level 2 on 29 March 2018, there has been a continued decline in the monitored parameters of Mayon Volcano. This is supported by the following observations;
1. Volcanic Earthquake Activity: For the past six months, seismic activity has declined to a daily average of one (1) 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.
2. Volcanic Gas Output: Sulfur Dioxide emission or SO2 flux from Mayon crater based on continuous gas spectrometry has stabilized between 300-700 tonnes/day since January 2020. The latest flux was measured at 229 t/d on 30 June 2020, considerably below the baseline of 500 t/d. The relatively low levels of SO2 flux indicate that passive degassing of stalled magma beneath the edifice has been transpiring.
3. Visual Observation of the Summit: Steaming activity from the crater has ranged from weak to moderate. A lava-dome presently occupies the crater but has not exhibited significant changes in configuration this year. Crater glow or incandescence associated with superheated gas escaping the summit vent has been faint and only visible through the aid of a telescope. 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.
4. Ground Deformation: In contrast to the above parameters, ground deformation measurements on Mayon remain anomalous. Geodetic data from continuous Global Positioning Systems (GPS) and electronic tiltmeters and campaign Electronic Distance Meter (EDM) and Precise Leveling indicate 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. 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.
In view of the above, PHIVOLCS-DOST is now lowering the alert status of Mayon from Alert Level 2 to Alert Level 1. This means that 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. In the event of a renewed increase in any one or combination of the above monitoring parameters, the alert status may step up once again to Alert Level 2. On the other hand, if there is a noticeable return to baseline levels of ground deformation and sustained low levels of other monitoring parameters, then the Alert Level may further step down. The public is still reminded to avoid entry into the 6-km Permanent Danger Zone or PDZ 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-DOST is closely monitoring Mayon Volcano’s activity and any new development will be immediately communicated to all concerned.
DOST-PHIVOLCS
