February 23, 2016
MANILA, Philippines – Two successive minor eruptions occurred at Bulusan Volcano in Sorsogon province yesterday afternoon, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).
Science research specialist Paul Alanis of the Phivolcs’ Volcano Monitoring Division said only one of the events spewed ash.
Alanis said both phreatic explosions happened at around 5:01 p.m. and lasted for less than five minutes.
He said one of the eruptions produced ash-laden steam clouds that rose up to 500 meters above “the active west-northwest vent.”
He said the grayish clouds of ash drifted towards west-southwest.
He noted that there were no rumbling sounds accompanying these events.
Alanis said traces of ash were reported at the towns of Juban and Irosin in Sorsogon following the eruptions.
According to Phivolcs, the heating of water by the magma underneath the volcano’s crater causes phreatic explosions or steam-driven eruptions that sends steam, water, and volcanic material out.
Due to the small explosive events at the volcano, Alanis said the current activity of Bulusan “is being closely monitored and evaluated by the agency.”
At present, he said the agency believes that the minor eruptions could be driven by hydrothermal activity happening beneath the volcano “that may lead to more steam-driven explosions.”
He noted that there were still no signs of a major eruption from Bulusan because they have not yet observed any magma intrusion.
Since no magmatic eruption is imminent, Alanis said Bulusan’s alert status will remain at level 1.
With alert level 1 hoisted over Bulusan, the public is not allowed to enter the four-kilometer permanent danger zone because of risk to sudden steam and ash explosions.
Due to the prevailing wind direction, Phivolcs said residents located in the northwest and southwest sectors of the volcano should take precautions against ashfalls.
The agency added that people residing near valleys and river channels should be vigilant against sediment-laden stream flows and lahars in the event of heavy and continuous rainfall.
Civil aviation authorities and pilots, on the other hand, are warned against flying close to the volcano’s summit as ejected ash and volcanic fragments from sudden explosions may pose hazards to aircraft.