Bulusan generates pyroclastic flow

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LEGAZPI CITY, Albay: Bulusan volcano ejected pyroclastic flow in two consecutive explosions recorded on Monday.

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Mount Bulusan erupted twice in eight minutes late on Sunday afternoon that rocked the towns of Irosin, Bulusan and Juban in Sorsogon province and other nearby towns.

The eruptions generated earthquakes, the first at 3:31 p.m. and the second eight minutes later, and lasted for a total of 15 minutes based on seismic records.

The first eruption originated from the summit crater and produced dirty-white to grayish ash column 2.5 kilometers high that drifted west-southwest.

This also generated small pyroclastic flow that cascaded down slopes approximately two kilometers from the summit.

Bulusan’s last eruption associated with pyroclastic flow was recorded some 30 years ago.

Traces of ash from Monday’s eruptions were noted in the villages of Gabao, Bulawan, Gulang-Gulang, Monbon, Cogon and Tinampo, all in Irosin town, while 0.5 millimeter thick ash was found in Barangay Bolos, Irosin and Barangay Caladgao in Juban town.

Ed Laguerta, resident chief volcanologist in Bicol of the Philippine Institute of Volcanology and Seismology (Phivolcs) said the thickest ash (1 millimeter) fell in Barangay Puting Sapa, Juban.

The volcano later exhibited a smaller eruption, originating from the southeast vent and producing a dirty-white to grayish ash column 500 meters above the vent.

Bulusan volcano has four craters.

A Phivolcs report said that rumbling sounds were heard in Gulang-Gulang, Tinampo, Monbon, Mapaso in Irosin town, while rumbling sounds accompanied by sulfur smells were experienced in Aniog and Putting Sapa, Juban.

For the past 24 hours, Bulusan’s seismic monitoring network recorded a total 33 volcanic earthquakes most of which occurred before the eruptions.

A noticeable increase in sulfur dioxide (SO2) emission to 578 tons a day was measured on Monday morning prior to the eruptions.

A few days ago, Phivolcs officials enforced a two-kilometer extended zone over Mount Bulusan in the southeast vents that pose a potential source of eruption close to the populated villages of Mapaso, as well as San Roque village in Bulusan town.

They said small-volume but hazardous pyroclastic density currents can potentially be generated by stronger steam-driven or phreatic eruptions and may travel down the Malunoy and Mapaso rivers, endangering the villages as well as Barangay Patag, Irosin.

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