Bulusan Volcano in the province of Sorsogon was placed under Alert Level 1 on Tuesday, May 11, due to a low level of unrest.

The volcano was previously under Alert Level 0 or normal.

The Philippine Institute of Volcanology and Seismology (Phivolcs) said in a bulletin on Tuesday evening that Bulusan Volcano’s monitoring network has recorded 124 volcanic earthquakes since Saturday, May 8.

“The increased seismicity could be followed by steam-driven or phreatic eruptions at the summit crater or from flank vents on the upper to middle slopes,” warned Phivolcs.

“Sustained inflation” or swelling of the volcano’s upper slopes has also been observed since March 6.

“These parameters indicate that volcanic processes are underway beneath the edifice that are likely caused by shallow hydrothermal activity,” Phivolcs said.

The agency reminded local government units and the public that entry into the Permanent Danger Zone surrounding Bulusan Volcano, a radius of four kilometers, “must be strictly prohibited.”

There is also an Extended Danger Zone, covering two more kilometers, where people must be vigilant “due to the increased possibilities of sudden and hazardous phreatic eruptions,” said Phivolcs. – Rappler.com