THE Philippine Institute of Volcanology and Seismology (Phivolcs) yesterday raised Alert Level 2 at Taal Volcano in Batangas because of “increased unrest” since February 13.
“This means that there is probable magmatic activity that may or may not lead to an eruption,” Phivolcs said in a bulletin raising the alert from Level 1 (low level unrest).
Phivolcs said it is not recommending evacuation but reminded residents that Taal Volcano Island is a permanent danger zone and entry to the island, especially at the main crater at the Daang Kastila fissure, is “strictly prohibited.”
Last month, Phivolcs announced a slight increase in Taal Volcano’s seismic activities, leading to the evacuation of hundreds of residents who have returned to the island after the volcano’s phreatic or steam-driven activity in January last year.
In its latest bulletin, Phivolcs advised local government units to continuously assess previously-evacuated barangays around Taal Lake for damage and road accessibility, and to strengthen preparedness, contingency, and communication measures in case of renewed unrest.
Phivolcs said that since February 13, it has recorded 28 volcanic tremor episodes, four low-frequency volcanic earthquakes, and one hybrid earthquake at shallow depths of less than 1.5 km beneath the Taal Volcano Island (TVI).
“Volcanic tremors have increased seismic energy compared to previously recorded episodes and ranged between three to 17 minutes in duration,” Phivolcs said.
It said the number of volcanic tremor events has risen to 866 since the onset of increased activity on 13 February.
“In addition to these, a total of 141 low-frequency volcanic earthquakes have occurred within one-kilometer depths beneath TVI and immediate vicinities. Overall, seismic activity in the past month indicates increased magmatic and hydrothermal activity at shallow depths beneath TVI,” Phivolcs added.
Phivolcs also observed changes in the main crater lake, noting it recorded in mid-February a temperature high of 74.6ºC and continuing increase in acidity to pH 1.59.
It also said said there is “ongoing slight deformation of TVI, center on a pressure source on its southeast sector.”