Bulusan Volcano Erupts in Sorsogon: Phreatic Explosion Triggers Alert Level 1

THE Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that the Bulusan Volcano in Sorsogon had a phreatic eruption on Monday morning.

PHIVOLCS Director Teresito Bacolcol said it occurred at 4:36 a.m. and lasted until 5 a.m.

The United States Geological Survey (USGS) described a phreatic eruption as a “steam-driven explosion.”

It occurs when magma heats the ground or surface water. It will then cause water to boil and flash into steam, which results in an explosion of water, steam, rock and ash.

During an interview aired over radio station DZBB, Bacolcol explained the nature of phreatic eruption more.

“Phreatic eruptions are steam-driven explosions that happen when water comes into contact with hot volcanic materials, pwedeng hot volcanic rocks or hot volcanic gases,” Bacolcol said.

“Ang nangyayari dito, it ejects steam, ash and rock fragments. Wala pong involved dito na panibagong magma,” he added.

He did not downplay the possibility of repetition of a phreatic eruption in the coming days.

“‘Yung steam-driven eruption kanina may be succeeded by the same similar events in the following days or following weeks,” he said.

Alert Level 1 in Sorsogon

Meanwhile, due to the incident, PHIVOLCS raised the alert level at Bulusan Volcano on Monday from Alert Level 0 to Alert Level 1.

This “means that the volcano is currently in a state of low-level unrest with chances of phreatic eruptions succeeding this morning’s event,” it said in a bulletin.

“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 PDCs, ballistic projectiles, rockfall, avalanches and ashfall on these danger areas,” it added.

PHIVOLCS also said of ashfall that occurred in Barangays Cogon and Bolos in Irosin, and Barangays Puting Sapa, Guruyan, Buraburan and Tulatula Sur in Juban.

See here for videos of ashfall.
See here for eruption.