Taal Volcano shows continued seismic activity – Phivolcs

Taal Volcano. Photo courtesy of Jillian Dumas.

LUCENA CITY — Taal Volcano in Batangas province continues to exhibit seismic activity, with volcanic earthquakes and tremors recorded in recent days, the Philippine Institute of Volcanology and Seismology (Phivolcs) reported on Wednesday.

In its bulletin, Phivolcs said two volcanic earthquakes were recorded over the past 24 hours. The quakes were accompanied by a volcanic tremor that lasted five minutes.

On Monday, eight earthquakes and five tremors—each lasting between two and four minutes—were also detected.

At least six earthquakes, accompanied by two tremors lasting between six and seven minutes, were recorded by state volcanologists on July 11.

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 described as “continuous seismic signals with regular or irregular oscillations and low frequencies (typically 0.5 to 5 Hz) that can last for more than a minute.”

“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,” Phivolcs added.

In its latest update, Phivolcs recorded the emission of 504 metric tons (MT) of sulfur dioxide from Taal’s main crater. The gas plume rose 600 meters before drifting east and northeast.

No upwelling of hot volcanic fluids was observed in the Main Crater Lake on Taal Volcano Island (TVI), locally known as “Pulo,” which sits at the center of Taal Lake.

Phivolcs also reported the absence of “vog,” or volcanic smog, during the latest observation.

According to the agency, stations of the Taal Volcano Network located on TVI have recorded a significant increase in real-time seismic energy measurements (RSAM) since July 6.

“The sharp increase in RSAM and the lack of observable degassing from the main crater may indicate blockage or plugging of volcanic gas pathways within the volcano, which may lead to short-term pressurization and trigger a phreatic or even a minor phreatomagmatic eruption,” Phivolcs said in an advisory last week.

The agency reminded the public that Alert Level 1 remains in effect over Taal Volcano, “which means that it is still in an abnormal condition and should not be interpreted as having ceased unrest or the threat of eruptive activity.”

“At Alert Level 1, sudden steam-driven or phreatic eruptions, minor phreatomagmatic eruptions, volcanic earthquakes, minor ashfall, and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within TVI,” Phivolcs said. /mcm/abc