The Philippine Institute of Volcanology and Seismology (Phivolcs) has not detected volcanic earthquakes in the Taal Volcano in the last 24 hours but a low-level background tremor has persisted since April 8.

Volcanic earthquakes last less than a minute, while volcanic tremors may last more than a minute, or even days.

In a volcano bulletin issued on Saturday, May 22, Phivolcs said that Taal Volcano continues to show "elevated unrest."

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"Activity at the main crater was dominated by upwelling of hot volcanic fluids in its lake which generated plumes that reached 1.5 kilometers tall before drifting to the southwest," Phivolcs said.

Moreover, the average daily sulfur dioxide (SO2) emission increased from 3,051 tonnes on Thursday, May 20, to 3,426 tonnes on Friday, May 21.

Meanwhile, temperature highs of 71.8°C and pH of 1.59 were last measured from the main crater lake on March 4, 2021 and Feb. 12, 2021, respectively.

"Ground deformation parameters from electronic tilt, continuous GPS and InSAR monitoring continue to record a very slow and steady inflation and expansion of the Taal region that began after the January 2020 eruption," Phivolcs said.

These parameters continue to indicate a persistent magmatic activity at shallow depths beneath the Taal Volcano.

As it continues to show signs of elevated unrest, Taal Volcano's status remains under Alert Level 2.

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," Phivolcs pointed out.

It reiterated that entry into the volcano island, which is a permanent danger zone, especially the vicinities of the main crater and Daang Kastila fissure, is strictly prohibited.

Occupancy and boating on Taal Lake should also be strictly prohibited, Phivolcs said.

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.