Phivolcs downgrades Bulusan Volcano's status to 'normal'
The Philippine Institute of Volcanology and Seismology (Phivolcs) on Wednesday, Aug. 18, lowered the alert status of Bulusan Volcano in Sorsogon from Level 1 or low-level unrest to Level 0 or normal.
"This means that observational parameters have returned to baseline levels and no magmatic eruption is foreseen in the immediate future," Phivolcs said.
It noted that volcanic earthquake activity declined to the baseline level of two to three earthquakes per day between July 1, 2021, and Aug. 17, 2021, during which a total of only 109 weak events were recorded.
"This indicates that rock fracturing within the volcanic system associated with shallow hydrothermal activity has diminished," Phivolcs said.
It also pointed out that ground deformation has been driven by tectonic processes rather than pressurization from subsurface magma.
Moreover, Phivolcs said that sulfur dioxide emission or SO2 flux from active vents on Bulusan remained below detection levels since May 6, 2021.
The last significant emission was recorded at 48 tonnes per day on May 20, 2021, which is well within the baseline level.
"Ambient carbon dioxide or CO2 concentrations in most monitored springs have weakened since April 2021 consistent with weak contributions from the shallow hydrothermal system or from deep magma degassing," it added.
When present, Phivolcs said the emission of steam plumes from the active vents on the upper Bulusan edifice has been very weak to weak, consistent with diminished hydrothermal activity.
However, it said that if a renewed increase in any one or combination of the monitoring parameters, the alert status may step up once again to Alert Level 1.
The public should avoid entry into the four-km permanent danger zone due to perennial hazards of rockfalls, avalanches, and sudden steam-driven or phreatic eruption from any of the active vents which may occur without warning.
Furthermore, people living in valleys and active river channels should remain vigilant against sediment-laden streamflows and floods in the event of prolonged and heavy rainfall.