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LEGAZPI CITY, Philippines – The Philippine Institute of Volcanology and Seismology (Phivolcs) disclosed on Friday, April 11, 2025, that sulfur dioxide (SO2) emissions from Mayon Volcano had jumped to 8,165 tonnes per day as of Thursday, April 10 — the second highest level recorded since volcanic gas concentrations began tapering off in mid-July last year. This sharp increase in gas output has prompted volcanologists to warn of a possible shift toward renewed eruptive activity at the summit crater, which could generate dangerous hazards around the volcano.
The elevated SO2 reading, measured by stationary ultraviolet spectrometry, is more than double the average daily emission of 4,196 tonnes observed since Mayon’s alert status was lowered to Alert Level 2 on August 5. Phivolcs noted that the spike was accompanied by a slight rise in low-frequency volcanic earthquakes (LFVQs), which are typically linked to degassing processes within the volcano’s conduit. While the real-time seismic energy release remains at background levels, the combination of higher gas flux and a small increase in LFVQs suggests that magma or hot fluids are moving closer to the surface.
Ground deformation adds to concern
In addition to the gas and seismic signals, electronic tilt measurements from the Mayon Volcano Network have detected a short-term trend of swelling or pressurization in the northern and eastern sectors of the volcano edifice. This deformation, together with the gas surge, reinforces the possibility that Mayon could enter a new phase of eruption in the coming days or weeks.
Phivolcs reiterated that the volcano remains under Alert Level 2 (moderate level of unrest), but cautioned that the current data “opens new possibilities of recurring eruptive unrest.” Under Alert Level 2, the public is strictly prohibited from entering the six-kilometer Permanent Danger Zone (PDZ) around the volcano. Local government units and communities located within predetermined pyroclastic density current (PDC) hazard zones are advised to review their emergency plans and be ready to respond if the alert status is raised to Alert Level 3.
What a new eruption could mean
A renewed eruptive phase could spawn life-threatening hazards, including pyroclastic density currents (PDCs) — fast-moving clouds of hot ash, rock, and gas — as well as rockfalls, ballistic fragments, and heavy ashfall. Phivolcs warned that prevailing poor weather conditions, common during the transition to the rainy season, could worsen the impacts of these hazards by reducing visibility and hampering evacuation efforts.
Ashfall, in particular, could affect communities downwind of the volcano, potentially disrupting air travel, damaging crops, and causing respiratory issues. The agency also urged communities to take preemptive measures against lahars (volcanic mudflows) and sediment-laden streamflows along channels that drain the volcano, especially during sustained heavy or intense rains — and in the event of a simultaneous explosive eruption.
Broader context and expert insight
The latest SO2 spike is reminiscent of degassing patterns observed before Mayon’s 2018 eruption, which forced thousands of residents to evacuate. According to the U.S. Geological Survey (USGS), sustained high SO2 emissions — often exceeding 5,000 tonnes per day — are a common precursor to magmatic eruptions at stratovolcanoes like Mayon. “When gas emissions rise sharply and are accompanied by seismic swarms or ground deformation, it often indicates that magma is ascending and degassing,” said Dr. Emily Carter, a volcanologist at the University of Hawaii who has studied Philippine volcanoes. “While not a guarantee of an eruption, it’s a signal that warrants close monitoring.”
Phivolcs continues to coordinate with the Office of Civil Defense and local disaster risk reduction councils to ensure that communities are informed and prepared. The agency has deployed additional monitoring equipment and is conducting round-the-clock visual and instrumental surveillance of the volcano.
Historical context and preparedness
Mayon Volcano, located in Albay province about 330 kilometers southeast of Manila, is one of the most active volcanoes in the Philippines. Its most recent major eruption occurred in 2018, when it spewed lava and ash for months, displacing tens of thousands of people. The current Alert Level 2 status indicates that the volcano is in a state of moderate unrest
