Alert Level Bulletin
16 March 2023
MAYON VOLCANO BULLETIN
16 March 2023
This serves as notice for the lowering of the alert status of Mayon Volcano from Alert Level 2 (Moderate Level of Unrest) to Alert Level 1 (Low Level of Unrest).
Since the start of the year, Mayon Volcano has exhibited a steady decline in its monitored parameters. This is supported by the following observations:
1. Volcanic Earthquake Activity: Volcanic earthquakes recorded by the Mayon Volcano Network (MVN) have declined to a daily average of 0-1 event/day since the first week of December 2022. Most of these occurred at depths of 6-10 kilometers beneath the eastern flanks and are attributed to rock fracturing processes within the volcano. In addition, rockfall from Mayon’s summit dome occurred during periods of intense rainfall over the summit area, rather than from extrusion of new dome lava at the crater.
2. Ground Deformation: Results from Precise Leveling (PL) campaign indicate that the Mayon edifice has been continuously deflating since July-August 2022. A localized short-term inflation of the middle to upper southeastern slopes was recorded by Global Positioning Systems (GPS), electronic tiltmeters and campaign Electronic Distance Meter (EDM) measurements since early February 2023; however, longer-term data suggest that the current ground deformation behavior of Mayon is largely driven by tectonic processes (e.g. earthquake activity in the Bicol region) rather than pressurization from volcanic sources.
3. Volcanic Gas Emission: Sulfur Dioxide emission or SO2 flux from Mayon crater based on continuous gas spectrometry has varied between a high 477 tonnes/day on 8 December 2022 to a low of 201 tonnes/day on 2 March 2023. The latest flux was measured at 312 tonnes/day on 8 March 2023. These SO2 emissions are considerably below the background level of 500 tonnes/day, and such relatively low levels are consistent with passive degassing of resting magma beneath the edifice.
4. Visual Observation of the Summit: Mayon’s summit crater has spewed only weak to moderate degassing plumes since the beginning of 2022. The summit lava dome, which grew a total extruded volume of 132,000 m3 between June and December 2022, has not exhibited further growth since. Crater glow, or incandescence associated with superheated gas emitted from the summit crater, has remained weak and visible only with the aid of a telescope. These observations of stable summit conditions are consistent with the absence of magma re-supply to the shallow levels of the edifice.
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 volcano’s state of unrest has declined to low levels and 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 unrest has completely ceased. 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 status 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. Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft. 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.