The Philippine Institute of Volcanology and Seismology (PHIVOLCS) on Monday recorded six volcanic earthquakes in Mt. Bulusan in Sorsogon that included a minor eruption at 5:01 pm.
PHIVOLCS said a high frequency earthquake was followed by low frequency earthquakes lasting four minutes and 21 seconds.
The agency said the eruption was phreatic, during which steam, and not lava, was ejected. It generated a short steam and ash column approximately 500 meters high.
Moderate emission of 50 meter-high white steam plumes was observed in the southwest and the west-northwest vent of the volcano.
The explosions were accompanied by a rumbling sound reportedly heard at Puting Sapa, Juban and Bolos, Irosin. However, prior to the eruption, PHIVOLCS detected no volcanic earthquake, although increased seismic activity was recorded on February 20 to 21.
Volcanic ashes were reported in the Barangay of Puting Sapa, Sagkayon, and Caladgao in Juban, and Bolos in Irosin.
PHIVOLCS reported that Alert level 1 remains in effect over Mt. Bulusan, indicating that hydrothermal processes are underway beneath the volcano that may lead to steam-driven eruptions.
The agency reminded the local government units and the public that entry to the 4-kilometer radius Permanent Danger Zone (PDZ) is strictly prohibited due to the possibility of sudden and hazardous steam-driven or phreatic eruptions.
PHIVOLCS also requested civil aviation authorities to advise pilots to avoid flying close to the volcano’s summit as ash from sudden phreatic eruption can be hazardous to aircraft.
People living within valleys and along rivers or stream channels especially on the southwest and northwest part of Bulusan were also warned to be vigilant against sediment-laden stream flows and lahar in the event of heavy and prolonged rainfall.