The Philippine Institute of Volcanology and Seismology (Phivolcs) on Friday, Feb. 6 lowered the alert status of Bulusan Volcano from Alert Level 1 to Alert Level 0 after monitoring data showed the volcano had returned to a “normal” state.

Bulusan had been under Alert Level 1 since April 28, 2025, before the downgrade announced in the agency’s 11 p.m. advisory on Feb. 6.

“Bulusan Volcano has returned to relative quiescence following a general decline in monitoring parameters,” Phivolcs said.

The agency said volcanic earthquakes recorded by the Bulusan Volcano Network have dropped to baseline levels of zero to five events per day since the first week of December 2025.

“The few recorded events have occurred at a shallow depth of less than 6 kilometers beneath the southeastern edifice,” Phivolcs said.

It added that the decline indicates rock-fracturing linked to shallow hydrothermal activity has diminished.

Ground deformation data also showed easing pressure beneath the volcano.

Phivolcs said the southern and eastern sectors have been deflating since late 2025, “indicating a depressurization of the volcanic system.”

Likewise, gas and heat emissions have returned to normal levels.

Phivolcs said sulfur dioxide output, which had averaged 122 tons per day since June 2025, “has since returned to background levels.”

It added that most monitored springs around the volcano have shown lower carbon dioxide concentrations, indicating that input from the shallow hydrothermal system “has remained within baseline level with only minor contributions if any from deep magma sources.”

Visual observations supported the downgrade, with plume activity at the summit described as “very weak to moderate” when present, consistent with baseline degassing.

Phivolcs said Alert Level 0 means that “no magmatic eruption is foreseen in the immediate future,” but warned that the alert status may be raised again if monitoring parameters increase.

Despite the downgrade, authorities reminded the public that entry into the four-kilometer radius permanent danger zone, particularly near vents on the south-southeastern slopes, should still be avoided due to the risk of sudden steam-driven or phreatic eruptions, rockfalls, and landslides.

Civil aviation authorities were also advised to keep aircraft away from the summit, while residents near valleys and river channels were urged to remain vigilant for possible sediment-laden flows and lahars during periods of heavy rain.