The Philippine Institute of Volcanology and Seismology (Phivolcs) reported increased seismic energy and record-high sulfur dioxide emissions at Mayon Volcano on Friday, Jan. 16, saying the activity could signal further eruptive developments.

In an advisory issued at 7:30 p.m., Phivolcs said a pronounced increase in real-time seismic amplitude measurement was recorded by three of the 16 stations in the Mayon Volcano Network between Thursday, Jan. 15, and Friday, despite the absence of volcanic earthquakes.

The rise was linked to increased rockfall and pyroclastic density current activity, locally known as “uson,” indicating higher rates of lava effusion at the summit crater.

Strong degassing was observed at the summit Friday morning, with sulfur dioxide emissions averaging 4,970 tons per day, which is the highest level recorded at Mayon in the past 15 years.

For comparison, the running average sulfur dioxide flux since Jan. 1 is 1,205 tons per day.

While real-time seismic energy levels have begun to decline as of advisory time, Phivolcs said the episode could forewarn of new magma intrusions into the Mayon edifice that may lead to further eruptive activity.

Mayon remains under Alert Level 3 as effusive eruption at the summit continues, the agency said, adding that the likelihood of lava fountaining or a moderately explosive eruption has slightly increased.

Ongoing lava effusion continues to generate lava flows, rockfalls, and collapse-fed pyroclastic density currents on the southern and eastern upper slopes, while possible lava fountaining or moderate explosions could affect all sectors of the volcano.

Phivolcs reiterated that entry into the six-kilometer-radius permanent danger zone remains prohibited and advised residents within the eight-kilometer radius to be prepared for possible evacuation should monitoring parameters suddenly escalate and the alert level be raised to Alert Level 4.

The agency also urged increased vigilance against lahars and sediment-laden streamflows along channels draining the volcano, as heavy rains are expected over Albay with the passage of Tropical Storm Ada (Nokaen).

Civil aviation authorities were likewise advised to keep aircraft away from the volcano’s summit due to the hazard posed by ash from any sudden eruption.