AS the Department of Science and Technology-Philippine Institute of Volcanology and Seismology (DOST-Phivolcs) assesses a possible extension of the permanent danger zone around Mayon Volcano, where recent pyroclastic density currents have been concentrated, it is important to note that months before the most intense volcanic activity, the monitoring and analytical systems used were already providing data for more accurate bulletins and faster response times.
Since the first magmatic phase on Jan. 6 was detected and intensified through the first quarter of the year, a combination of seismic instrumentation, satellite-based deformation measurements, gas emission tracking and terrain-informed hazard modeling, with increasing use of automated data processing, provided early warning to local government units and the general public through the VolcanoPH app.
Seismic monitoring was carried out through the Mayon Volcano Network, consisting of 16 broadband stations transmitting continuous ground motion data. Real-time Seismic Amplitude Measurement remained the standard metric for tracking overall energy release, but signal interpretation incorporated machine learning models trained on historical eruption datasets. These models classified seismic signals into high-frequency tectonic events and low-frequency volcanic earthquakes, which are associated with magma movement and gas resonance within the conduit.
In early February 2026, the number of low-frequency events increased sharply, reaching 1,346 within a single reporting period. This increase was incorporated into interpretive models linking seismic patterns with eruptive behavior. Collapse-generated pyroclastic density currents observed shortly afterward were consistent with these interpretations, indicating that signal classification contributed to short-term hazard assessment.
Deformation data provided an independent line of evidence. Ground-based Global Navigation Satellite System stations recorded displacement in near real-time, while time-series Interferometric Synthetic Aperture Radar measurements were used to detect millimeter-scale changes in surface elevation. From mid-2024 to early 2026, radar data indicated sustained inflation concentrated along the eastern and northeastern flanks of the volcano. This pattern is consistent with continued magmatic intrusion rather than transient pressurization. When considered together with seismic observations, the deformation data supported the interpretation of magma accumulation at depth and upward migration toward the surface.
Gas emission measurements were used to further constrain subsurface conditions. Sulfur dioxide output during the first quarter of 2026 averaged 2,466 tons per day, with a peak of 6,569 tons recorded on Feb. 4. Elevated sulfur dioxide emissions indicate that magma has reached shallow levels, allowing dissolved gases to escape as pressure decreases.
Phivolcs evaluated gas flux in relation to seismicity and deformation rates to assess conduit conditions. Concurrent high gas output and sustained seismic activity are consistent with an open conduit system, which favors lava effusion and periodic collapse events rather than immediate large-scale explosive activity.
Activity during this period also included secondary hazards associated with lava flow emplacement. Along the Basud and Bonga channels, extending approximately 3.8 kilometers and 1.6 kilometers, respectively, phreatic explosions were recorded where water interacted with active lava. These events result from rapid phase changes as water is converted to steam, fragmenting lava into fine ash. Although localized, such events extend hazard zones beyond the summit area and require monitoring of rainfall, flow advance and surface temperature.
Data from these monitoring systems were integrated through the GeoRiskPH framework, including the Handa platform. The system combines seismic classifications, deformation measurements, gas emissions, digital elevation models and rainfall data to produce scenario-based outputs. These include projected runout distances for lava flows and pyroclastic density currents, as well as lahar susceptibility estimates based on the volume of unconsolidated material and rainfall intensity thresholds. Outputs are updated as new data are received, allowing for continuous revision of hazard estimates.
Information was disseminated through situation reports, hazard advisories and technical bulletins. These documents translate monitoring data into short-term forecasts tied to specific hazards, including ashfall distribution, lava flow advance, pyroclastic density current reach and lahar potential. Ashfall projections incorporated plume observations and wind data to identify affected areas and likely deposition patterns. Lahar advisories identified river systems with accumulated volcanic material and assessed the likelihood of sediment mobilization during rainfall events.
These outputs were used by local government units in Albay to support operational decisions. Evacuation zones were adjusted in response to updated runout projections, particularly as lava flows advanced and collapse hazards increased. Lahar advisories were issued in advance of rainfall events based on sediment load estimates, leading to temporary restrictions in river channels and adjacent areas.
As of this writing, the volcano remains under Alert Level 3, with monitoring conducted on a daily basis using seismic data, visual observations and runout modeling. According to Phivolcs Director Teresito Bacolcol, any adjustment will depend on whether collapse-generated flows become more widespread or extend farther downslope.
DOST Secretary Renato Solidum Jr. said conditions do not indicate an explosive eruption, noting that the observed “uson” events are consistent with lava accumulation and gravitational collapse rather than sustained eruptive columns. The current activity is classified as effusive, with lava extrusion at the summit leading to periodic collapses that generate short-lived pyroclastic density currents. These are distinct from column-collapse events associated with explosive eruptions.
A shift to Alert Level 4 would require broader escalation, including stronger explosions, sustained lava fountaining, increased seismicity and more frequent or widespread pyroclastic flows. The proposed expansion of the danger zone is a targeted response to observed flow behavior and modeled runout distances. Implementation will depend on local government units, which may carry out additional evacuations in areas identified as at risk based on updated hazard projections.
