Increased seismic activity, crater lake changes at Taal –PHIVOLCS

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) on Monday said it recorded a slight increase in tremors and changes at the main crater lake of Taal Volcano in Batangas.

In an advisory, PHIVOLCS said Taal Volcano’s monitoring network recorded a series of 50 relatively weak tremor episodes beginning 5 a.m. until 3 p.m. on Monday.

“These tremor episodes ranged in duration from two to five minutes and occurred at shallow depths of less than 1 kilometer, signaling increased hydrothermal activity beneath Taal Volcano Island,” it said.

Since Saturday, PHIVOLCS said a total of 68 shallow tremor episodes occurred on the island.

Moreover, geochemical data on the main crater lake indicated continuous acidification of lake water from a pH 2.79 to pH 1.59 between January 2020 and February 2021.

“[A]n unseasonal temperature high of 77º C and CO2/H2S gas flux ratios consistent with shallow magma degassing,” PHIVOLCS added.

“Ground deformation data from continuous electronic tilt on Volcano Island record a slight deflation localized around the main crater, although very slight inflation from GPS data and InSAR analysis and positive microgravity changes have been steadily recorded across the Taal region consistent with continuous magmatic degassing and hydrothermal unrest.”

Further, PHIVOLCS reminded the public that Taal Volcano remained under Alert Level 1 (abnormal).

PHIVOLCS warned that “there are increased possibilities of sudden steam-driven or phreatic explosions, lethal accumulations or expulsions of volcanic gas and minor ash fall from the main crater that can occur and threaten areas within the Volcano Island.”

“DOST-PHIVOLCS strongly recommends that entry into TVI, Taal’s permanent danger zone or PDZ, especially the vicinity of the main crater and the Daang Kastila fissure, must remain strictly prohibited,” it said. — Ma. Angelica Garcia/DVM, GMA News