October 7, 2016
MANILA, Philippines – A minor phreatic ash eruption occurred at Bulusan Volcano in Sorsogon province before dawn yesterday, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).
In its bulletin, Phivolcs said the low-energy ash ejection event happened at 3:03 a.m. and lasted for about 15 minutes.
The agency said this event was accompanied by “short harmonic tremor” and rumbling sounds that were heard by residents of Barangay San Roque in Bulusan town.
Phivolcs noted that it did “not observed visually” how high the ejected ash-laden steam clouds due to thick clouds covering the summit.
However, the agency said traces of ash were reported at Barangay Inlagadian in Casiguran town and in barangays Rizal, Buenavista, Gubat proper, Tugawe, Tigkiw, Ariman, Bintuco, Bulacao, and Naagtan at Gubat town.
From 5 a.m. Wednesday until 4 p.m. yesterday, Phivolcs said at least 42 volcanic quakes were recorded in Bulusan.
Christian Clarito, science research specialist of the Phivolcs Volcano Monitoring Division, said the minor eruption could be driven by hydrothermal activity happening beneath the volcano.
Clarito said the heating of water by the magma underneath the volcano’s crater causes phreatic explosion or steam-driven eruption that sends steam, water, and volcanic material out.
Due to the small explosive event at the volcano, he said Bulusan is being closely monitored by the agency.
At present, Clarito said Bulusan will remain at alert level 1.
Alert level 1 means that no major magmatic explosion is imminent, but steam-driven explosions can still occur.
Due to the possibility of sudden steam-driven or phreatic eruptions, Phivolcs reminded the public not to enter the volcano’s four-kilometer permanent danger zone.
The agency also advised people residing near valleys and river channels, especially on the southwest and northwest sectors of the edifice, to be vigilant against sediment-laden stream flows and lahars in the event of heavy and continuous rainfall.
Civil aviation authorities have also been told to warn pilots against flying close to the volcano’s summit as ejected ash and volcanic fragments from sudden phreatic eruption may pose hazards to aircraft.
On Wednesday, Phivolcs warned communities in the southern sector of Bulusan against the harmful effects of volcanic gases and ash.
The agency issued the warning after it validated reports from some residents that the volcano’s fissure on the southeast summit slopes emitted a low-lying steam plume with small amounts of ash and released a foul odor last September 30.
Micah Sayco, science research specialist of the Phivolcs Volcano Monitoring Division, said residents of Brgy. Mapaso in Irosin town had complained of foul smell of “rotten eggs” until Wednesday afternoon.
Sayco said most volcanic gases do not only smell bad, but also “hazardous to human health and may even cause fatality.”
She noted that short-term effects of exposure to volcanic ash and toxic fumes such as sulfur dioxide (SO2) could already lead to irritation of eyes and respiratory tract.
She added that inhalation of SO2 could also cause headaches, cough, and people with asthma may suffer airway constriction.
Sayco further noted that other volcanic gases have the potential to cause loss of consciousness and in extreme cases, may lead to asphyxiation. -RBL