LUCENA CITY - Seismic activity continued to be recorded at Taal Volcano in Batangas province, the Philippine Institute of Volcanology and Seismology (Phivolcs) said on Monday, Sept. 8.

In its morning bulletin, Phivolcs reported that state volcanologists detected 21 volcanic earthquakes over the past 24 hours. These were accompanied by 16 volcanic tremors lasting two to four minutes.

From Sept. 1 to 8, Taal Volcano registered a total of 86 volcanic earthquakes and 78 volcanic tremors.

Phivolcs defines volcanic earthquakes as those "generated by magmatic processes or magma-related processes beneath or near an active volcano."

"Unlike tectonic earthquakes that are produced by faulting, volcanic earthquakes are directly produced by many processes and are therefore much more varied in characteristics," the agency explained.

Volcanic tremors, on the other hand, are "continuous seismic signals with regular or irregular oscillations and low frequencies (typically 0.5-5 Hz) that can last for more than a minute," Phivolcs said.

"Tremor can be caused by different processes inside the volcano, including resonance triggered by magma or magmatic gas flowing through cracks and vents, successive overlapping low-frequency earthquakes, and eruptions of magma," it added.

In its latest update, Phivolcs recorded the emission of 3,356 metric tons of sulfur dioxide from Taal's main crater, which rose 750 meters high. The agency classified the activity as a "weak emission."

It added that no upwelling of hot volcanic fluids was observed in the main crater lake of Taal Volcano Island, located in the middle of the Taal Lake.

No volcanic smog, or vog, was also detected during the latest monitoring period.

READ: Taal Volcano logs 13 quakes as seismic activity rises

Alert Level 1, or low-level unrest, remains in effect over Taal Volcano.

Phivolcs warned that sudden steam-driven or phreatic eruptions, minor phreatomagmatic activity, ashfall, and the release of volcanic gas may occur.

Authorities continue to prohibit entry into Taal Volcano Island, the volcano's permanent danger zone, particularly within the main crater and the Daang Kastila trail. Flying any aircraft over the island is also discouraged, as ash from sudden eruptions may pose hazards.

Taal Volcano last erupted in January 2020, more than four decades after its previous eruption, prompting hundreds of thousands to evacuate from within the 14-kilometer danger zone.

Taal is the country's second most active volcano, with 38 recorded historical eruptions./mcm