PHIVOLCS places Mt. Bulusan on Alert Level 1 due to volcanic activity

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) on Sunday placed the Bulusan Volcano on Alert Level 1 due to increased volcanic activity.

“Bulusan Volcano entered a period of low-level unrest with a sustained series of volcanic earthquakes that began on 15 March 2026. Since then, a total of four hundred seventy-five (475) volcanic earthquakes has been recorded by the Bulusan Volcano Network (BVN). Most of these were weak volcano-tectonic earthquakes that are associated with rock fracturing at shallow depths beneath the volcano edifice and are similar in general characteristics to seismicity prior to the June 2022 and April 2025 eruptions,” PHIVOLCS said in its 12 p.m. Volcano Bulletin.

Alert Level 1 means that the volcano is currently in a state of low-level unrest with increased chances of phreatic eruptions. 

State seismologists added “ground deformation data from continuous GPS and electronic tilt monitoring indicate inflation or swelling of the western and southeastern flank since the last week of January and first week of March 2026, respectively. Degassing activity from the active vents when visible has been weak to moderate, consistent with weak volcanic sulfur dioxide or SO2 emission as indicated by below background averages of 91 tonnes/day measured on 17 March 2026.” 

PHIVOLCS warned these parameters could indicate that shallow hydrothermal processes beneath the volcano are underway that could lead to steam-driven or phreatic eruptions at any of its summit vents.

Local government units and the public were reminded that entry into the 4-kilometer radius Permanent Danger Zone (PDZ) is strictly prohibited and that vigilance should be observed in the 2-kilometer Extended Danger Zone (EDZ) on the southeast sector due to the possible impacts of volcanic hazards such as pyroclastic density currents or PDCs, ballistic projectiles, rockfall, avalanches and ashfall on these danger areas. 

Authorities also advised communities on Bulusan’s west side to prepare for ashfall in case phreatic eruption occurs, paying special attention to vulnerable members of the community including the elderly, expecting mothers, infants and those with medical conditions. 

Civil aviation authorities are advised to inform pilots to avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft. 

“Furthermore, people living within valleys and along river/stream channels especially on the southeast, southwest and northwest sector of the edifice should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall should phreatic eruption occur,” PHIVOLCS warned.

PHIVOLCS said it is closely monitoring Bulusan Volcano’s condition and any new development will be relayed to all concerned. 

Located in the province of Sorsogon in the Bicol Region, Mount Bulusan is 70 kilometers southeast of Mayon Volcano and approximately 390 kms. southeast of Metro Manila. —RF, GMA Integrated News