LEGAZPI CITY, Albay — Mount Mayon is showing another worrying sign of renewed volcanic unrest after its sulfur dioxide emissions suddenly surged to 8,393 tonnes per day, the highest level recorded since the decline in volcanic gas concentrations began in July.
The sharp increase was recorded on August 17, 2026, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS). The agency said the latest reading was significantly higher than the average 2,532 tonnes per day recorded from August 5, when Mayon was downgraded to Alert Level 2, through August 16.
The development has raised concern because the increase in sulfur dioxide came alongside a short-term trend of swelling or pressurization on the northern and eastern portions of the volcano, based on electronic tilt measurements from the Mayon Volcano Network.
PHIVOLCS: POSSIBLE RENEWED ERUPTIVE ACTIVITY
PHIVOLCS warned that the elevated sulfur dioxide emissions could be a sign that Mayon is moving toward another phase of eruptive activity at its summit crater.
The agency has not declared a new eruption, however, and Mayon remains under Alert Level 2, which indicates moderate volcanic unrest.
Still, PHIVOLCS said renewed activity could produce potentially life-threatening hazards, including pyroclastic density currents, rockfalls, ballistic fragments and extensive ashfall.
Pyroclastic density currents—locally known as uson—are particularly dangerous because they can move rapidly down volcanic slopes carrying extremely hot gas, ash and debris.
The warning comes only days after Mayon briefly produced an ash plume on August 12, which was observed around 6:03 p.m. and drifted toward the northeast.
WHY THE 8,393-TON READING MATTERS
The latest sulfur dioxide reading is significant not simply because of its size, but because of the sudden change in the volcano’s behavior.
PHIVOLCS noted that the August 17 measurement was the highest recorded since volcanic gas concentrations began declining on July 16.
The increase also follows the lowering of Mayon’s alert status from Level 3 to Level 2 on August 5, when officials determined that the volcano’s overall unrest had decreased enough to warrant the downgrade.
But the latest measurements show why the situation remains closely monitored.
GMA News likewise reported that PHIVOLCS considers the abrupt rise in SO2 emissions a possible warning of renewed eruptive activity. The agency also noted that volcanic seismicity and real-time seismic energy release remained at background levels at the time of its advisory.
That distinction is important: the sulfur dioxide spike does not automatically mean a major eruption is imminent. Rather, it is one of several indicators volcanologists monitor when assessing changes in a volcano’s activity.
MAYON COULD ERUPT AGAIN IN THE COMING DAYS
The Philippine Information Agency reported Tuesday that state volcanologists see a possibility that eruptive activity could recur in the coming days.
PHIVOLCS has therefore urged residents, local governments and other authorities near Mayon to remain prepared in case unrest intensifies and the alert level is raised again to Alert Level 3.
The agency has also emphasized that the 6-kilometer Permanent Danger Zone remains off-limits.
Authorities are particularly concerned about the possibility of lahars and sediment-laden flows during periods of heavy or prolonged rainfall. Rain can mobilize loose volcanic materials deposited on Mayon’s slopes and channels, creating dangerous flows even when no eruption is occurring.
MAYON’S VOLCANIC ACTIVITY HAS BEEN PERSISTENT
The latest warning comes after months of significant activity from the country’s most active volcano.
Mayon’s 2026 activity included prolonged effusive and Strombolian eruptions that began earlier in the year and resulted in the evacuation of thousands of residents. The volcano’s activity later declined sufficiently for PHIVOLCS to lower its alert status to Level 2 in August.
Earlier in July, Mayon also recorded a much larger sulfur dioxide spike. Philstar reported that the volcano emitted an average of 13,128 tonnes of sulfur dioxide per day on July 11, described by PHIVOLCS at the time as its highest level since 2000.
The latest 8,393-ton reading is therefore below that July peak, but it is still significant because it represents a sharp rebound after weeks of declining volcanic gas concentrations.
WHAT RESIDENTS SHOULD WATCH FOR
For communities around Mayon, authorities are urging vigilance rather than panic.
PHIVOLCS advises the public to:
- Stay outside the 6-kilometer Permanent Danger Zone.
- Follow evacuation and emergency instructions issued by local authorities.
- Remain alert during periods of intense or prolonged rainfall because of possible lahars.
- Prepare for possible ashfall and other volcanic hazards if activity increases.
- Avoid flying close to the summit because sudden eruptions could send ash and ballistic fragments into the air.
For now, Mayon remains at Alert Level 2.
But the sudden jump in sulfur dioxide emissions, combined with signs of swelling on parts of the volcanic edifice, has put authorities on heightened watch.
The crucial question now is whether the latest gas surge will fade—or become the first warning sign of another eruptive phase.
PHIVOLCS continues to closely monitor Mayon and has said that further developments will be communicated to authorities and the public.
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