MANILA, Philippines — The Philippine Institute of Volcanology and Seismology (Phivolcs) has reminded the public to avoid the 4-kilometer radius permanent danger zone of Mt. Bulusan in Sorsogon province, after it raised the volcano’s alert status on Sunday morning.
In a bulletin issued at 11:10 a.m. on Sunday, Phivolcs raised the volcano’s status to abnormal, or Alert Level 1, following an increase in seismic activity over the weekend.
16 volcanic quakes
A total of 16 volcanic quakes were recorded by the Bulusan seismic monitoring network, while data from April 29 to May 5 showed “slight inflation” of the upper slopes.
Phivolcs also observed “wispy to weak” emission of white steam plumes from its southeast vents and recorded a notable rise in water temperature in hot springs.
According to the bulletin, the abnormal status indicates that hydrothermal processes may be underway beneath the volcano, and that these may lead to steam-driven eruptions.
Vigilance
Following the elevated status, the agency called for vigilance in the extended danger zone, which stretches to two kilometers downslope of the permanent danger zone, for possible sudden and hazardous phreatic eruptions, as well as landslides and rockfalls.
Pilots are advised to avoid flying close to the volcano’s summit as ash from phreatic eruptions could harm aircraft.
Phreatic eruptions occur when magma hits ground or surface water, causing an explosion of water, steam, rock and ash.
“People living within valleys and along river/stream channels should be vigilant against sediment-laden stream flows and lahars in the event of heavy and prolonged rainfall,” Phivolcs said.
Bulusan’s last phreatic eruption was recorded in June 2017. Its alert level was lowered to zero in August 2018. —Jhesset O. Enano