MANILA, Philippines — Bulusan Volcano in Sorsogon is again under Alert Level 1.
The Philippine Institute of Volcanology and Seismology (Phivolcs) raised the alert status of the volcano yesterday, citing increased hydrothermal activity, an indication of overall unrest.
“Phivolcs is raising the alert status of Bulusan from Alert Level 0 to Alert Level 1, which means that the volcano is currently in a state of low-level unrest,” the agency said in an advisory.
A total of 126 weak and shallow volcanic earthquakes were recorded on Tuesday, most of which occurred in the northwestern sector and summit area of the volcano.
Phivolcs also cited a ”pronounced and ongoing inflationary trend” in Bulusan since Sept. 22, which signifies ongoing pressurization of the shallow hydrothermal system.
It said volcanic carbon dioxide concentrations have been increasing since July 22 while temperature in the hotsprings on the southwestern sector have been rising since April.
Residents of Sitio Talistison in Barangay Mapaso in Irosin and Barangay San Roque in Bulusan reported sulfurous odor.
Entry into the four-kilometer-radius permanent danger zone is strictly prohibited and vigilance in the two-kilometer extended danger zone on the southeast sector is advised.
Phivolcs said residents living within valleys and along river stream channels of the volcano should be vigilant.
It said sediment-laden stream flows and lahar in the event of heavy and prolonged rainfall may be expected should phreatic eruption occur.
The Civil Aviation Authority of the Philippines said it served notice to airmen following the raising of Bulusan’s alert level.
Phivolcs placed Bulusan under Alert Level 1 on June 5 after recording a phreatic eruption that lasted for 17 minutes, which forced dozens of families to evacuate their homes.
The alert level was lowered to zero in August after the volcano calmed down.