Taal Volcano's elevated unrest continued with the detection of 355 earthquakes and upwelling of "hot volcanic fluids" in the past 24 hours, the Philippine Institute of Volcanology and Seismology (Phivolcs) said in its report released on Wednesday, May 12.
Of the total volcanic earthquakes, Phivolcs said Taal Volcano had 201 low-frequency earthquakes and 154 volcanic tremor events with durations of two to 35 minutes, and low-level background tremor that persisted since April 8, 2021.
It also observed an upwelling of hot volcanic fluids in the Taal Lake which generated 200-meter tall but weak plumes that drifted to the southwest.
Taal Volcano's sulfur dioxide emission also increased from 2,325 tonnes on Monday, May 10, to 3,463 tonnes on Tuesday, May 11.
Meanwhile, temperature highs of 71.8 degrees Celsius and pH of 1.59 were last measured from the main crater lake on March 4 and Feb. 12, 2021, respectively.
Phivolcs added that ground deformation parameters continued to indicate a "very slow and steady inflation and expansion of the Taal region that began after the January 2020 eruption."
"These parameters indicate persistent magmatic activity at shallow depths beneath the edifice," it said.
"Alert Level 2 (increased unrest) is currently maintained over Taal Volcano, but elevated unrest has recurred in the past 48 hours and volcano conditions remain unstable," Phivolcs pointed out.
The restive volcano in Batangas has been under Alert Level 2 since March 9, 2021.
"Sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ashfall, and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within and around TVI (Taal Volcano Island)," Phivolcs pointed out.
It warned the public from entering the volcano island, which is a permanent danger zone, especially the vicinities of the main crater and Daang Kastila fissure.
Occupancy and boating on Taal Lake should also be strictly prohibited, Phivolcs added.
Local government units were advised to continuously assess and strengthen the preparedness of previously evacuated barangays around Taal Lake in case of renewed unrest.
Civil aviation authorities were also asked to advise pilots to avoid flying close to the volcano as airborne ash and ballistic fragments from explosions and wind-remobilized ash may pose hazards to aircraft.