Seismic activities continue to be detected in four active volcanoes which manifest that they are still under "abnormal" state.
During their 24-hour observation period from Saturday to Sunday, Philippine Institute of Volcanology and Seismology (Phivolcs) seismic monitoring networks recorded 12 volcanic earthquakes in Bulusan Volcano, 11 in Kanlaon Volcano, two in Mayon Volcano, and seven in Taal Volcano.
These volcanoes are still under Alert Level 1 due to their "abnormal status," but only a "low level of volcanic unrest" is currently detected.
In the past 24 hours, very weak emission of white steam-laden plumes from the southeast vents was also observed from the Bulusan Volcano.
Phivolcs' ground deformation data from continuous GPS measurements indicate slight inflation on the edifice since July 2020, while the long-term trend since May 2019 denotes that the edifice is still deflated
"These parameters indicate that volcanic processes are underway beneath the edifice that may be caused by deep-seated degassing or hydrothermal activity or magmatic intrusion," it said.
Local government units surrounding the Bulusan Volcano were advised to strictly enforce the no-entry policy into the four-kilometer radius Permanent Danger Zone (PDZ), and into the two-kilometer extended danger zone on the southeastern sector of the volcano.
In Kanlaon Volcano, Phivolcs observed a weak to moderate emission of white steam-laden plumes that rose 300 meters then drifted northwest, northeast, and southwest.
Sulfur dioxide (SO2) emission was measured at an average of 500 tons per day as of Sept. 26.
Ground deformation data from continuous GPS measurements also indicate slight inflation of the lower and mid slopes since May 2020, while short-term electronic tilt monitoring on the southeastern flanks recorded inflation on the lower to mid slopes that began on June 21, 2020.
"These parameters may indicate hydrothermal or magmatic processes occurring beneath the edifice," Phivolcs said.
Entry into the four-kilometer radius PDZ must be strictly prohibited due to the further possibilities of sudden and hazardous steam-driven or phreatic eruptions, it advised.
Phivolcs also observed moderate emission of white steam-laden plumes that crept from the downslope of Mayon Volcano before drifting northeast.
"Faint crater glow from the summit could be observed at night. Sulfur dioxide (SO2) emission was last measured at an average of 506 tons per day on Sept. 20, 2020," it said.
Phivolcs also detected slight inflation of the edifice using its ground deformation data. Electronic tilt data also indicated non-steady inflation of the middle to upper edifice that began in late 2019.
"This follows an inflationary trend that has been recorded by continuous GPS monitoring since the middle of 2019," it added.
Although Mayon Volcano is under Alert Level 1, it means that presently no magmatic eruption is imminent.
However, it still strongly advised the public to refrain from entering the six-kilometer radius PDZ due to the perennial life-threatening dangers of rockfalls, landslides and avalanches at the middle to upper slope, sudden ash puffs, and steam-driven or phreatic eruptions from the summit.
In Taal Volcano, weak steaming or fumarolic activity rising 20 meters high before drifting northeast was observed from vents on its main crater in the past 24 hours.
Sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ashfall, and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within the Taal Volcano Island, Phivolcs advised.
It recommended that entry into the Taal Volcano Island, Taal’s PDZ, especially the vicinities of the main crater, and the Daang Kastila fissure, must remain strictly prohibited.