The Philippine Institute of Volcanology and Seismology (Phivolcs) detected an "increased activity" at Bulusan Volcano in Sorsogon due to "shallow hydrothermal processes" in the past few days.

In a volcano advisory issued on Monday evening, May 10, Phivolcs said a total of 62 volcanic earthquakes were recorded at Mt. Bulusan since Friday, May 7.

It also manifested steady inflation of the upper slopes of the edifice since March 6, 2021.

"Ground deformation data from continuous GPS measurements indicate a short-term slight inflation since February 2021 while the long-term trend from July 2019 denotes that the edifice is still deflated," Phivolcs pointed out.

At present, Phivolcs said, "only very weak to weak emission of white steam-laden plumes could be observed at the southeast vents."

"The increased seismic activity and short-term ground deformation are likely caused by shallow hydrothermal processes beneath the edifice," it noted.

While it has monitored an increased activity, Phivolcs said Bulusan Volcano remains under Alert Level 0 or normal status

However, its current status is subject to change should current activity persist, it added.

"Since hydrothermal processes are underway beneath the volcano, there are increased chances of steam-driven or phreatic eruptions from its active vents," Phivolcs said.

It advised the local government units and the public to prevent from entering the four-kilometer radius permanent danger zone.

"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," Phivolcs said.

Moreover, people living within valleys and along river/stream channels especially on the southeast, southwest, and northwest sector of the edifice were asked to stay vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall.