MANILA, Philippines — The Philippine Institute of Volcanology and Seismology (PHIVOLCS) has reported a renewed increase in seismic activity at Bulusan Volcano in Sorsogon. Over a 24-hour monitoring period ending Thursday, April 23, 2026, the bureau recorded a significant uptick in volcanic earthquakes, signaling intensified hydrothermal activity beneath the edifice.
While the volcano remains under Alert Level 1 (Low-level Unrest), state volcanologists are closely monitoring the situation for potential steam-driven or phreatic eruptions.
The latest bulletin from PHIVOLCS highlighted several indicators of unrest:
- Volcanic Earthquakes: A total of 28 volcanic earthquakes, including weak background tremors, were recorded. This is a notable increase from the single-digit counts observed earlier in the week.
- Degassing: Moderate plumed emissions reaching up to 200 meters high were observed drifting toward the northwest and southeast.
- Ground Deformation: Continuous GPS and tilt monitoring indicate a slight inflation of the southern upper slopes, suggesting pressurized fluids or volcanic gases are moving within the system.
PHIVOLCS reminded the public and local government units that the following restrictions remain strictly in effect:
- 4-Kilometer Permanent Danger Zone (PDZ): Entry into the 4-km radius PDZ is strictly prohibited due to the constant threat of sudden and hazardous phreatic eruptions.
- Extended Danger Zone (EDZ): Vigilance is advised within the 2-kilometer Extended Danger Zone on the southeast sector, as this area is susceptible to sudden volcanic activity.
- Aviation Warning: Civil aviation authorities are advised to instruct pilots to avoid flying close to the volcano’s summit, as ash from any sudden eruption can be hazardous to aircraft.
The Sorsogon Provincial Disaster Risk Reduction and Management Office (PDRRMO) has been placed on blue alert. Local officials are currently:
- Reviewing Evacuation Plans: Coordinating with barangays within the high-risk zones to ensure that evacuation routes are clear.
- Health Advisories: Reminding residents in downwind communities to prepare N95 masks or wet cloths in case of ashfall, which can cause respiratory irritation.
- Monitoring Water Sources: Checking for potential contamination of local springs or rivers due to increased volcanic sulfur emissions.
PHIVOLCS emphasized that under Alert Level 1, the primary threat is a phreatic eruption—a sudden explosion driven by steam when water beneath the ground is heated by magma or hot rocks. These events can occur without significant warning and can eject ash, steam, and large rock fragments.
Residents are encouraged to stay updated through official PHIVOLCS social media channels and local news outlets to avoid misinformation.