The Bulusan Volcano in Sorsogon erupted on Monday morning, April 28, 2025, sending a steam-filled plume 500 meters into the air.
PHIVOLCS raised Alert Level 1 following the eruption.
Phivolcs said the eruption was phreatic or steam-driven, and lasted 24 minutes, starting at 4:36 am.
The grayish-white plume drifted northwest, affecting surrounding areas.
Phivolcs said a pyroclastic flow, known locally as uson, moved about 3 kilometers from Bulusan’s summit.
These flows are fast-moving and dangerous, made up of hot gas, ash, and broken rocks rushing down the volcano.
About 15 minutes before the eruption, local officials heard rumbling sounds, which were also picked up by Phivolcs’ special sensors.
Communities near the volcano, especially in Juban and Irosin, were advised to remain vigilant.
PHIVOLCS warned the public against entering the four-kilometer Permanent Danger Zone (PDZ), citing risks of sudden explosions and ashfall.
Bulusan Volcano in Sorsogon is one of the Philippines’ most active volcanoes.
It often has sudden steam-driven explosions that can happen without warning.
Bringing dangers like ashfall, fast-moving volcanic flows, and mudflows to nearby areas.
PHIVOLCS assured the public that it continues to monitor the volcano through seismic stations, satellite imagery, and ground observations.
PHIVOLCS maintained that Alert Level 1 does not mean an eruption is imminent, but steam-driven explosions could still occur without warning.
A pyroclastic flow, known locally as uson, is a fast-moving mixture of hot gas, ash, and broken rocks that rushes down the volcano. In this eruption, the flow moved about 3 kilometers from the summit, posing serious hazards to surrounding areas.
Alert Level 1 means that the volcano is exhibiting low-level unrest. This does not mean an imminent eruption, but there is a possibility of steam-driven explosions and other volcanic activity, such as ashfall and pyroclastic flows.
While the eruption has subsided, PHIVOLCS continues to monitor the situation closely. Further steam-driven explosions could still occur without warning.
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