Bulusan Volcano Experiences Phreatic Eruption
Bulusan Volcano in Sorsogon underwent a phreatic eruption early Monday morning, as confirmed by the Philippine Institute of Volcanology and Seismology (PHIVOLCS). The phreatic eruption began at 4:36 a.m. and lasted until 5 a.m., releasing a plume that reached up to 4.5 kilometers high. This plume drifted west to southwest from the crater.
A phreatic eruption is a steam-driven explosion caused when magma heats underground or surface water. According to a local volcanic expert, “Ang nangyayari dito, it ejects steam, ash and rock fragments. Wala pong involved dito na panibagong magma.” (What happens here is that steam, ash, and rock fragments are ejected. No new magma is involved.)
Understanding the Nature of Phreatic Eruption
Phreatic eruptions occur without the release of new magma. Instead, intense heat causes water to boil or instantly turn into steam, leading to explosive bursts of steam, ash, and rock fragments. These events can precede, accompany, or follow a more traditional volcanic eruption.
Experts warn that the recent phreatic eruption may be followed by similar events in the coming days or weeks. “‘Yung steam-driven eruption kanina may be succeeded by the same similar events in the following days or following weeks,” the expert explained.
Alert Level Raised Following Phreatic Eruption
Following the eruption, PHIVOLCS raised Bulusan Volcano’s alert status from Alert Level 0 to Alert Level 1. This indicates that the volcano is in a state of low-level unrest with a chance of additional phreatic eruptions.
Authorities urge local governments and residents to stay clear of the permanent danger zone, defined as a four-kilometer radius from the crater. They also advise vigilance within the 2-kilometer extended danger zone in the southeast sector, due to possible hazards such as pyroclastic density currents, rockfalls, avalanches, ballistic projectiles, and ashfall.
Ashfall and Safety Precautions
Recent ashfall has affected nearby barangays, including Cogon and Bolos in Irosin, as well as Puting Sapa, Guruyan, Buraburan, and Tulatula Sur in Juban. Residents experiencing ashfall are encouraged to wear protective masks or cover their noses and mouths with wet cloths to avoid inhaling ash particles.
Additionally, a pyroclastic density current, locally called “uson,” descended the volcano’s southwestern slopes, traveling approximately three kilometers from the summit. Due to the hazards posed by ash clouds, nearby air traffic is advised to avoid flying close to the volcano.
Ongoing Volcanic Activity and Monitoring
Before the eruption, Bulusan Volcano experienced 53 volcanic earthquakes on Sunday. Local officials reported hearing rumbling sounds about 15 minutes before the eruption, which were detected by infrasound sensors.
People living in valleys and along river or stream channels on the southeast, southwest, and northwest sectors are urged to be cautious of sediment-laden flows and lahars, especially during heavy or prolonged rainfall, should further phreatic eruptions occur.
For more updates on Bulusan Volcano phreatic eruption, visit Filipinokami.com.