The Kanlaon Volcano in Negros Island may be raised to Alert Level 2 status after logging an increased seismic activity in the area, including gas emission, said the Philippine Institute of Volcanology and Seismology on Wednesday.
Kanlaon has been showing signs of unrest as it exhibited a total of 15 volcano-tectonic earthquakes between 3:58 a.m. and 5:00 a.m. on 22 November.
Phivolcs said the Alert Level 1 status of the Kanlaon volcano remains, but it may be raised to Alert Level 2 should the unrest activities increase.
"The public is reminded that Alert Level 1 prevails over Kanlaon. Should the above uptrend in monitoring parameters persist, the volcano status may be raised to Alert Level 2 to warn of increasing unrest," Phivolcs said in its latest advisory.
It noted that these earthquakes ranged in energy from magnitude 1.4 to magnitude 4.2 and occurred at depths of 0 to 2 kilometers beneath the northern flank of the Kanlaon range.
With its current conditions, the volcano may pose sudden steam-driven explosions or phreatic eruptions as its emission of volcanic sulfur dioxide or SO2 from the summit crater has increased since 18 July— averaging 570 tonnes daily since 1 May, with the latest SO2 measurement on 14 November averaging 1,017 tonnes daily.
Phivolcs said the ongoing volcano-tectonic earthquake activities indicate that fracturing at deeper levels is occurring and may possibly lead to further unrest.
The monitoring parameters in the past months have been consistent with shallow hydrothermal activity driven by degassing of deeper magma.
While the ongoing volcanic-tectonic earthquake activity indicates shallow rock-fracturing on the edifice which may lead to further unrest.
The Kanlaon volcano remains at low-level unrest wherein a slight increase in volcanic earthquake and steam or gas activity has been observed, with volcanic plume emission being logged at 200 meters moderately drifting southeast.
Phivolcs said the ground deformation data from continuous GPS and electronic tilt measurements have been recording shorter-term inflation of the southwestern middle slopes since October 2023 and longer-term inflation of the entire edifice since March 2022.
It also strongly advised the public and local government units to be vigilant.
Entering a four-kilometer permanent danger zone near the volcano remains prohibited due to increased chances of sudden and hazardous phreatic eruptions occurring without warning.
Flying any aircraft close to the volcano is likewise not allowed due to increased chances of sudden and hazardous phreatic eruptions occurring without warning.