The Philippine Institute of Volcanology and Seismology (Phivolcs) on Friday, July 30, 2021, lowered the alert level status of Mayon Volcano from 1 to 0 as monitored parameters are back to normal levels.
Mayon Volcano has been at Alert Level 1 or abnormal status since July 17, 2020.
Phivolcs explained that lowering Phivolcs’ alert status from Alert Level 1 to Alert Level 0 means that “observational parameters have returned to baseline levels and no magmatic eruption is foreseen in the immediate future.”
It noted that the frequency of volcanic earthquakes has declined to baseline levels–about zero to five events per day–for the last six months, which indicates that “rock-fracturing within the volcanic edifice associated with magmatic or hydrothermal activity has diminished.”
“The integrated global positioning systems, electronic distance measurement, precise leveling, and electronic tilt data indicate ground deformation that is more coherent with local tectonic processes rather than pressurization from a magmatic or hydrothermal source,” it also pointed out.
Moreover, Phivolcs said sulfur dioxide emission or SO2 flux from the Mayon crater has declined below the baseline level of 500 tonnes per day since July 14, 2021.
The latest flux was measured at 156 tonnes per day on July 14 and “no plume has been detected since.”
“The relatively low levels of SO2 flux indicate that passive degassing from stored magma beneath the edifice is diminishing or increasingly scrubbed by Mayon’s hydrothermal system,” Phivolcs explained.
Faint crater glow, or incandescence associated with superheated gas emission at the summit vent, continues to be observed but only through a camera. Its last visibility with the naked eye was in May 2021.
Phivolcs said Mayon Volcano’s plume emission from the crater has been weak to moderate this year.
In addition, no changes in the summit lava dome extruded in the final phase of the 2018 eruption were observed during the past year.
“These observations are consistent with diminished magma degassing and the absence of magma intrusion within the edifice,” it pointed out.
However, Phivolcs said that in the event of a renewed increase in any one or combination of the Mayon Volcano’s monitoring parameters, “the alert status may step up once again to Alert Level 1.”
The public is still reminded to avoid entry into the six-kilometer permanent danger zone due to perennial hazards of rockfalls, avalanches, ash puffs, and sudden steam-driven or phreatic eruption at the summit area, which may occur without warning.
Likewise, people living in valleys and active river channels are asked to remain vigilant against sediment-laden streamflows and lahars in the event of prolonged and heavy rainfall.