Bulusan Volcano Put on Alert Level 1

(PNA) –- The Philippine Institute of Volcanology and Seismology (Phivolcs) on Thursday raised the alert level on Mount Bulusan, an active volcano in Sorsogon in the Bicol region as it was observed that it generated a steam-driven explosion from a vent on its northwest upper slopes that propelled an ash plume.

In its 8 a.m. advisory, Phivolcs is raising the Alert Level of Bulusan Volcano from Alert Level 0 (normal) to Alert Level 1 (abnormal) which indicates that hydrothermal processes may be underway beneath the volcano that may lead to more steam-driven eruptions.

During the observation, around 9:46 p.m. on Thursday (May 6, 2015), Bulusan Volcano (12.7667°N, 124.0500°E) in Sorsogon Province generated a steam-driven explosion from a vent on its northwest upper slopes that propelled an ash plume approximately 250 m high before it drifted west.

The explosion event lasted 3.5 minutes based on the seismic records. Traces of ash were observed in Sitio Tulay of Brgy. Bagsangan, Cogon, Monbon, and Tinampo in Irosin, Sorsogon.

According to Philvocs, the event was preceded by a similar steam-driven explosion from the same vent on May 1, 2015 that lasted for five minutes.

Based on past records, more explosions can be expected to occur with varying intensity, duration and distribution of ash.

Phivolcs Director Renato Solidum Jr, explained that steam-driven eruptions, called “phreatic” eruptions, occur when water makes contact with hot rock inside the volcano causing steam. Due to pressure build-up, the steam escapes through the crater explosively.

Such explosions are typical to Bulusan during restive periods, when its hydrothermal system is disturbed or when steam accumulates and pressurizes at the shallow levels of the volcanic edifice.

This indicates that hydrothermal processes may be underway beneath the volcano that may lead to more steam-driven eruptions.

With this development, the agency noted the local government units and the public are reminded 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.

The civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ash from any sudden phreatic eruption can be hazardous to aircraft. Furthermore, people living within valleys and along river/stream channels should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall. DOST-PHIVOLCS is closely monitoring Bulusan Volcano’s condition and any new development will be relayed to all concerned.

Mount Bulusan is about 70 km southeast of Mayon Volcano, which is in Albay, and about 250 km southeast of Manila, the capital of the Philippines.

In June 2014, Mayon started showing heightened volcanic activity. By September, Phivolcs had raised Alert Level 3, prompting precautionary evacuation of residents in areas near the volcano.

But by December, with its volcanic activity diminished, Phivolcs lower its warning to Alert Level 2 and evacuees were allowed to return home.

However, the residents are still advised not to venture in the 6-kilometer permanent danger zone. (PNA) FPV/CLTC/Brian Joseph N. Morales/BJNM (OJT)