MANILA, Philippines — The Philippine Institute of Volcanology and Seismology on Sunday urged caution as it raised Alert Level 1 over Mount Bulusan in Sorsogon due to increased seismic activity and increased water temperature.
In its Bulusan Volcano Bulletin on Sunday morning, Phivolcs said it has recorded 16 volcanic earthquakes between May 4 and May 5. It also noted that tilt data from April 29 to May 5 shows a slight inflation of the upper slopes of the volcano.
According to US Geological Survey, monitoring the tilt or slope angle as well as shape or "strain" helps volcanologists keep an eya on moving magma.
"There is also a notable increase in water temperature from the monitored hot springs while wispy to weak emission of white steam plumes was observed from the southeast vents," Phivolcs said Sunday.
The agency said that raising Alert Level 1 (abnormal) "indicates that hydrothermal processes may be underway beneath the volcano that may lead to steam-driven eruption."
It also reminded local government units and residents near the volcano that entry to the 4-kilometer Permanent Danger Zone around the volcano should be avoided.
It also urged vigilance in the Extended Danger Zone, which is two kilometers beyond the PDZ, "due to the possibiities of sudden and hazardous phreatic eruptions (steam but no lava), rockfall and landslide."
Phivolcs said aircraft should avoid flying close to the volcano's summit because of ash from an eruption is hazardous to aircraft.
"Furthermore, people living within valleys and along river or stream channels should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall," it also said.
Phivolcs is monitoring Bulusan Volcano closely and said it will relay developments to the public.