Overview: Bulusan Volcano Shows Increased Seismic Activity
The Bulusan Volcano in Sorsogon is experiencing a rise in seismic activity, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS). The agency reported a notable number of volcanic earthquakes within a 24-hour period and noted ongoing gas emissions from the volcano’s vents. While the alert level remains at Level 1, indicating low-level unrest, PHIVOLCS cautions that steam-driven or phreatic eruptions could occur suddenly and without warning.
Seismic Signals and What They Mean
PHIVOLCS said that 72 volcanic earthquakes were recorded by the Bulusan Volcano Network starting at midnight on Saturday, October 11. The majority of these events are volcano-tectonic (VT) earthquakes, which are linked to rock fracturing within the volcano. The quakes are occurring at depths of less than 10 kilometers beneath the northern sector of Bulusan. A cluster of shallow VT earthquakes often signals magma movement and deformation in the near-surface environment, though not all such activity leads to an eruption. The current VT activity is being monitored closely as a potential precursor to more significant unrest.
Gas Emissions and Hydrothermal Activity
PHIVOLCS also noted ongoing degassing from Bulusan’s active vents, ranging from very weak to weak during days when the volcano was visible. On Thursday, October 9, the volcano emitted an average of about 31 tonnes of sulfur dioxide (SO2). This figure is well below Bulusan’s baseline of around 200 tonnes per day, suggesting a shallow hydrothermal system beneath the volcano rather than a large, magma-driven surge. The combination of VT earthquakes and modest degassing points to continued shallow hydrothermal activity beneath the summit.
Current Alert and What It Means for the Public
PHIVOLCS has maintained Bulusan at Alert Level 1, which indicates low-level unrest rather than an imminent eruption. Nonetheless, the agency warns that steam-driven or phreatic explosions could occur suddenly and without warning, ejecting steam, volcanic ash, and volcanic bombs from the crater or its vents. Residents and visitors should stay informed through PHIVOLCS advisories and local government updates.
Hazards Within the Danger Zones
PHIVOLCS emphasized the importance of staying away from the four-kilometer Permanent Danger Zone (PDZ) around Bulusan, and to exercise vigilance in the two-kilometer Extended Danger Zone (EDZ) on the southeast flank. Potential hazards in these zones include pyroclastic densities currents (PDCs), ballistic projectiles, rockfalls, ashfall, and other volcanic phenomena. While large eruptions are not currently expected, the possibility of sudden activity means residents, farmers, and travelers should be prepared to alter plans if advisories change.
Protective Measures and Community Guidance
In response to evolving conditions, PHIVOLCS recommends practical safety steps for communities, especially during ashfall, which can irritate the eyes and respiratory system. People should use protective masks or a wet cloth to cover the nose and mouth, particularly for the elderly, individuals with respiratory or cardiovascular issues, pregnant women, and infants. It is also advised to monitor air quality and avoid unnecessary exposure to the ash plume if it is observed upwind of inhabited areas. For those near the summit or within the EDZ, flight paths and sources of access to the crater area should be avoided to reduce risk from sudden emissions.
What to Expect Next
Scientists will continue to analyze seismic data, gas emissions, and ground deformation to assess whether Bulusan’s unrest is intensifying. The current information suggests ongoing shallow hydrothermal activity with no immediate eruption forecast, but evolving conditions could alter this assessment. Local authorities will issue updates if there are changes in the alert level or new advisories for residents and travelers in Sorsogon and nearby provinces.
Conclusion: Staying Informed and Prepared
Bulusan’s latest activity underscores the importance of local vigilance and adherence to official warnings. While the risk of a sudden eruption remains low at present, the possibility of steam-driven eruptions and ash release requires communities and visitors to stay prepared and informed. By following PHIVOLCS advisories and respecting the PDZ and EDZ boundaries, residents can reduce exposure to potential volcanic hazards while continuing to monitor the situation as scientists refine their assessments.
