SORSOGON, Philippines – Disaster management authorities in the towns of Irosin and Juban in Sorsogon province evacuated more than 1,000 people on Thursday, May 7, amid the twin threats of a pending volcanic eruption and an approaching typhoon.
Government volcanologists raised the alert level on Mount Bulusan in Sorsogon early Thursday after the volcano, one of the most active in the Philippines, erupted twice in a week.
The weather bureau, meanwhile, said it expected to raise Storm Signal No. 1 over Sorsogon and 3 other provinces in the Bicol region by 11 pm of Thursday.
On Wednesday night, after Bulusan erupted a second time in a week, some residents around the volcano already fled their houses.
Director Renato Solidum of the Philippine Institute of Volcanology and Seismology (Phivolcs) warned that a series of explosions is possible for Bulusan, and that lahar from its slopes might remobilize in the low lying areas following the threat of intense rainfall expected toward the weekend.
The ashes emitted by Bulusan fell on the volcano’s southwest quadrant, particularly on the towns of Juban and Irosin. Traces of ash were observed in Sitio Tulay of Barangay Bagsangan, Cogon, Monbon, and Tinampo in the municipality of Irosin.
Solidum 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,” Solidum said.
This indicates that hydrothermal processes may be underway beneath the volcano that may lead to more steam-driven eruptions.
To ensure the safety of the public, Phivolcs strictly warned local government units and the public not to enter the 4-kilometer radius Permanent Danger Zone (PDZ). There is a possibility of sudden and hazardous steam-driven or phreatic eruptions in the coming days, it said.
Phivolcs also told civil aviation authorities to advise pilots to avoid flying close to the volcano’s summit, as ash from any sudden phreatic eruption can be hazardous to aircraft.
Mount Bulusan is one of the active volcanoes in the country. Sometime between 2005 and 2006, the two active volcanoes in the Bicol region – Bulusan in Sorsogon and Mayon in neighboring Albay province – both became restive and erupted.
Currently, Mount Mayon is on alert level 2 and may erupt anytime once magma shoots up toward the crater rim. Phivolcs scientists are closely watching both volcanoes. – Rappler.com
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