Bulusan Volcano was downgraded back to Alert Level 0 on Wednesday, August 18, more than three months since Alert Level 1 was raised last May 11.
Alert Level 0 means the volcano in Sorsogon has returned to a normal state, coming from low-level unrest.
The Philippine Institute of Volcanology and Seismology (Phivolcs) said on Wednesday that there has been “a general decline in monitoring parameters.”
These parameters include:
- Volcanic earthquakes: Two to three weak earthquakes were recorded per day between July 1 and August 17, for a total of only 109. “This indicates that rock fracturing within the volcanic system associated with shallow hydrothermal activity has diminished.”
- Ground deformation: This has been “driven by tectonic processes rather than pressurization from subsurface magma.”
- Gas emission: Sulfur dioxide emission has stayed “below detection levels” since May 6, while “ambient carbon dioxide concentrations in most monitored springs have weakened” since April.
- Surface activity: Emission of steam plumes has been very weak to weak.
While Phivolcs said “no magmatic eruption is foreseen in the immediate future,” Alert Level 1 could be raised again for Bulusan Volcano if any of the parameters increase.
Phivolcs also reminded the public not to enter the 4-kilometer permanent danger zone surrounding Bulusan Volcano.
There could be rockfalls, avalanches, and steam-driven or phreatic eruptions “which may occur without warning.”
“Furthermore, people living in valleys and active river channels are cautioned to remain vigilant against sediment-laden streamflows and floods in the event of prolonged and heavy rainfall,” added Phivolcs. – Rappler.com