MANILA, Philippines — The Philippine Institute of Volcanology and Seismology (Phivolcs) on Wednesday raised Alert Level 1 on Mt. Kanlaon in Negros Occidental, an indication that it is in an abnormal condition and period of unrest.
In its 10 a.m. bulletin, Phivolcs said that Kanlaon’s seismic monitoring network recorded 80 volcanic earthquakes since March 9, which was dominated by 77 low-frequency events associated with “magmatic fluids beneath the edifice.”
The seismic activity, Phivolcs added, could be followed by steam-driven or phreatic eruptions at the volcano’s summit crater despite the absence of “visible degassing or steaming from the active vent” this year.
“Ground deformation data from continuous GPS measurements indicate a period of long-term slow inflation of the edifice since 2017, while short-term electronic tilt monitoring on the southeastern flanks recorded slow inflation of the lower slopes since May 2019 and pronounced inflation of the upper slopes in the end of January 2020,” the bulletin read.
Phivolcs stated that the aforementioned parameters indicate that volcanic processes are “underway deep beneath the edifice,” which may be caused by deep-seated degassing or hydrothermal activity or magmatic intrusion.
With Alert Level 1 raised, Phivolcs reminded concerned local government units and law enforcement authorities that entry into the four-kilometer radius Permanent Danger Zone (PDZ) is strictly prohibited due to possible steam-driven or phreatic eruptions.
A phreatic eruption is a “steam-driven explosion that occurs when hot volcanic materials come in contact with water.”
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Civil aviation authorities must also be advised to avoid flying close to the volcano’s summit, as ejecta—or material that is explosively ejected from a volcano—from any sudden phreatic eruption pose aviation hazards.
Mt. Kanlaon, which is the centerpiece of Mt. Kanlaon Natural Park, last erupted in June 2016.