Taal Volcano has become more active and could have a “magmatic” eruption soon, the Philippine Institute of Volcanology and Seismology said on Wednesday.
Phivolcs said the famous volcano in Batangas has recorded 2,015 volcanic tremors, 734 low-frequency volcanic earthquakes, and 18 hybrid earthquake events since February 13, as seismic activity in the area had an "elevated increase."
The agency said that "harmonic tremor associated with magma migration" was the dominant type of earthquake since March 19.
"Most earthquake events occurred at shallow depths of (less than) 2 kilometers although some large earthquakes were generated in the deeper 2-6 kilometers region beneath the Taal Volcano Island (TVI) edifice," Phivolcs said.
"Overall seismic energy release has markedly increased since yesterday afternoon compared to previous seismic swarms," it added.
There are two types of volcanic eruptions in terms of activity — explosive and effusive. Explosive eruptions are characterized by gas-driven explosions that propels magma and tephra. Effusive eruptions, meanwhile, are characterized by the outpouring of lava without significant explosive eruption.
Magmatic eruptions produce juvenile clasts during explosive decompression from gas release, geologists say. They range in intensity from the relatively small lava fountains on Hawaii to catastrophic Ultra-Plinian eruption columns more than 30 kilometers high, bigger than the eruption of Mount Vesuvius in 79 AD that buried Pompeii in Italy.
Taal’s sulfur dioxide gas emission in the previous week has been generally high with a peak of 1,184 tons per day last Sunday, the state seismology bureau noted.
These parameters indicate that magmatic eruption may be possible, it said.
"Ground deformation of TVI and the Taal Caldera region, in general, has remained steady and at slight inflationary trends since February 2021," it said.
"The above parameters indicate that magma has been migrating across shallow depths beneath TVI, increasing the possibilities of magmatic eruption."
The alert level is still at the second mark or "increased unrest," Phivolcs said.
It recommended that entry into Taal Volcano Island, Taal’s Permanent Danger Zone or PDZ, especially the vicinities of the Main Crater and the Daang Kastila fissure, and occupancy and boating on Taal Lake, must be strictly prohibited.
"Local government units are advised to continuously assess and strengthen the preparedness of previously evacuated barangays around Taal Lake in case of renewed unrest," it said.
"Civil aviation authorities must advise pilots to avoid flying close to the volcano as airborne ash and ballistic fragments from sudden explosions and wind-remobilized ash may pose hazards to aircraft."