THE Philippine Institute of Volcanology and Seismology (Phivolcs) has reported an increase in seismic activity at Mayon Volcano in Albay, which could in turn increase the chances of steam-driven or phreatic eruptions.
Mayon Volcano remains under Alert Level No. 1 which, Phivolcs said, means it is still in an “abnormal condition.”
In an advisory issued at 5:30 p.m. on Saturday, Phivolcs said it has recorded 26 volcanic earthquakes at Mayon Volcano since 12 a.m. of Saturday. In the past weeks, Phivolcs said, it recorded zero to two volcanic earthquakes a day.
The 26 volcanic quakes, Phivolcs said, had magnitudes ranging from 0.4 to 2.7, and “most originated at depths of 5-10 kilometers beneath the northeast flank of the Mayon edifice.”
“Mayon has been exhibiting non-uniform inflation or swelling in its northeastern sector since October 2024 and its south to southwestern sectors since March 2025 based on continuous GPS (global position system), electronic tilt and EDM (Exposure Database Mapper) ground deformation data,” Phivolcs said.
“Sulfur dioxide SO2 emissions have remained near background levels, averaging 430 tonnes/day this year with the latest measurements on 3 September 2025 averaging 609 tonnes/day,” Phivolcs also said.
Phivolcs said the increase in seismicity and the longer-term swelling of Mayon’s edifice “could indicate that deep magma intrusion may be taking place beneath the volcano, which could increase the chances of steam-driven or phreatic eruptions occurring at the crater.”
Although Under Level 1 means no magmatic eruption is imminent, the public is strongly advised to refrain from entering the six-kilometer permanent danger zone because of life-threatening hazards such as rockfall, landslides/avalanches, ballistic projectiles and short pyroclastic density (PDCs) currents or ‘uson’ that could be generated by a sudden phreatic eruption from the summit,” Phivolcs said.
It said stream or river channels and lahar-prone areas should also be avoided especially during heavy and prolonged rainfall.
“Civil aviation authorities must advise pilots to avoid flying close to the volcano’s summit as airborne ash and ballistic fragments from sudden explosions and PDCs may pose hazards to aircraft,” Phivolcs said.
In an interview with the radio dzMM on Saturday night, Phivolcs director Teresito Bacolcol said the increase in seismic activities is “a concern but not at the level of lava eruption.”
“The activity only shows that the volcano is restless and the main concern right now is the possibility of sudden phreatic eruption which can occur anytime without warning,” he said.
“That’s why we are reminding the public not to go inside the six-km permanent danger zone,” he added.
Bacolcol said phreatic eruptions are possible at Mayon Volcano, even at Alert Level 0, as long there are “right ingredients.” He was referring to water and hot volcanic materials.
Phivolcs said phreatic eruptions are “steam-driven explosions that occur when water beneath the ground or on the surface is heated by magma, lava, hot rocks, or new volcanic deposits.”
