Bulusan erupts, Alert Level 1 raised

(UPDATE) ALERT Level 1 has been raised over Bulusan Volcano in Sorsogon province following a Monday morning explosion that lasted for 24 minutes as ashfall events were reported in the towns of Juban and Irosin.

This image released by the Philippine Institute of Volcanology and Seismology shows ash emissions at the summit crater of Kanlaon Volcano on March 6, 2025. PHIVOLCS-DOST PHOTO

The Philippine Institute of Volcanology and Seismology (Phivolcs) director Teresito Bacolcol said Mount Bulusan's eruption, which was described as phreatic, began at 4:36 a.m. and lasted until 5 a.m.

Bacolcol also said that prior to the phreatic eruption, a total of 53 volcanic earthquakes were recorded over the last 24 hours in the area.

The volcanic event also produced a bent plume that rose 4,500 meters above the crater before drifting west to southwest, Bacolcol said.

"Rumbling sounds were reported by local government officials approximately before the eruption and were recorded by infrasound sensors," the Phivolcs chief said.

Alert Level 1 means the volcano is at low-level unrest with increased chances of steam-driven or phreatic eruptions, Bacolcol said.

He explained that phreatic eruption happens when water comes into contact with hot volcanic materials (either rocks or gases), producing steam, ash and sometimes fragmented volcanic materials.

A phreatomagmatic eruption, on one hand, occurs when magma interacts with water, causing explosive events that produce a mix of steam, ash, and fragmented volcanic materials, it added.

Phreatomagmatic eruptions tend to be more powerful since there is already direct contact with magma.

Dong Mendoza, spokesman of the Sorsogon provincial government, told The Manila Times that the eruption affected residents in the towns Juban and Irosin and ashfall incidents were reported in the villages of Cogon and Bolos in Irosin and Puting Sapa, Guruyan, Buraburan and Tulatula Sur in Juban.

Mendoza said that they are currently conducting a ground survey to assess the impact of the eruption to the communities in Juban and Irosin.

Mount Bulusan in Sorsogon has a summit elevation of 1,565 meters (5,135 feet). It is a stratovolcano located on the Irosin caldera, covering the northeast rim of a caldera formed approximately 40,000 years ago.

Local government units and the public are reminded that entry into the 4-kilometer radius permanent danger zone (PDZ) is strictly prohibited and that vigilance in the 2-kilometer extended danger zone (EDZ) on the southeast sector must be exercised due to the possible impacts of volcanic hazards such as pyroclastic density currents, ballistic projectiles, rockfall, avalanches and ashfall on these danger areas.