The Philippine Institute of Volcanology and Seismology (Phivolcs) has recorded 14 volcanic earthquakes in Mt. Kanlaon during its 24-hour monitoring from Sunday, Feb. 21 to Monday, Feb. 22.
Aside from volcanic earthquakes, Phivolcs also detected sulfur dioxide emission, measuring an average of 587 tonnes per day on Feb. 17, 2021.
In its volcano bulletin issued at 8 a.m. Monday, Phivolcs said ground deformation data from continuous GPS (global positioning system) and electronic tilt measurements have been recording a slight inflation of the lower and middle slopes since June 2020, it added.
"These parameters may indicate hydrothermal, tectonic, or deep-seated magmatic processes occurring deep beneath the edifice," Phivolcs said.
As of Monday, Mt. Kanlaon remains under Alert Level 1, which means it is still in an abnormal condition but at a low level of unrest.
The local government units and the public were reminded to refrain from entering the four-kilometer permanent danger zone due to a continuing possibility of sudden and hazardous steam-driven or phreatic eruption.
In the past 24 hours, Phivolcs was also able to detect six tremor episodes having durations of one to four minutes in Taal Volcano.
It also observed weak emission of white steam-laden plumes from "fumarolic" activity at the vents of the main crater.
Temperature highs of 74.6 degrees Celsius and pH of 1.59 were last measured from the main crater lake, respectively, on Feb. 18 and Feb. 12, 2021, Phivolcs added.
"Ground deformation parameters from continuous electronic tilt on volcano island record a slight deflation around the main crater since October 2020 but overall, very slow and steady inflation of the Taal region has been recorded by continuous GPS data after the eruption," it noted.
With these observations, Phivolcs said Taal Volcano remains under Alert Level 1 due to possible sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ashfall, and lethal accumulations or expulsions of volcanic gas that can occur and threaten areas within the Taal Volcano island.
Phivolcs strongly discourages entry into the Taal volcano island, which is a permanent danger zone, especially the vicinities of the main crater and the Daang Kastila fissure.
The local government units were also advised to continuously assess previously evacuated barangays around Taal Lake for damages and road accessibilities and to strengthen preparedness, contingency, and communication measures in case of renewed unrest.
People were asked to observe precautions due to ground displacement across fissures, possible ashfall, and minor earthquakes.
Phivolcs also recommended civil aviation authorities to advise pilots to avoid flying close to Mt. Kanlaon and Taal Volcano as airborne ash and ballistic fragments from sudden explosions and wind-remobilized ash may pose hazards to aircraft.