The alert status of Taal Volcano was raised from Alert Level 1 (low level of unrest) to Alert Level 2 (increasing unrest), PHIVOLCS reported on its bulletin on Tuesday, March 9.
Since 13 February 2021, Taal Volcano has been exhibiting increased unrest based on the following monitoring parameters:
- Volcanic Earthquakes. The Taal Volcano Network (TVN) recorded a total of twenty-eight (28) volcanic tremor episodes, four (4) low frequency volcanic earthquakes, and one (1) hybrid earthquake at shallow depths of less than one and a half (1.5) kilometers beneath Taal Volcano Island or TVI in the past 24 hours. Volcanic tremors have increased seismic energy compared to previously recorded episodes and ranged between three (3) to seventeen (17) minutes in duration. The total 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 (LFVQs) have occurred within one (1) 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.
- Changes in the Main Crater Lake (MCL). Survey observations in mid-February 2021 recorded a temperature high of 74.6ºC and continuing increase in acidity to pH 1.59 from a pH of 2.79 in January 2020 of the MCL. Increasing acidity is caused by sustained volcanic gas input into the shallow hydrothermal system that feeds into the lake, signifying degassing of magma intruded at depth during the January 2020 eruption.
- Ground Deformation. Integrated real-time ground tilt and continuous GPS and daily Electronic Distance Measurement (EDM) monitoring and Interferometric SAR (InSAR) data analysis indicate ongoing slight deformation of TVI centered on a pressure source on its southeast sector. Continuous GPS and InSAR data further yield a very slow but steady inflation and/or expansion of the Taal region since the end of the 2020 eruption, at very much slower and stabilized rates compared to deformation before and right after the eruption.
- Microgravity Changes. Campaign surveys have measured positive microgravity changes across Taal Caldera after the 2020 eruption consistent with density changes caused by magma migration, magma degassing and hydrothermal activity.
Taal Volcano raised to Alert Level 2 due to ‘increasing unrest’ – PHIVOLCS
In view of the above, DOST-PHIVOLCS is now raising the alert status of Taal from Alert Level 1 to Alert Level 2. This means that there is probable magmatic activity that may or may not lead to an eruption.
At Alert Level 2, evacuation is not yet recommended. However, the public is reminded that Taal Volcano Island is a Permanent Danger Zone (PDZ) and that entry into TVI, especially the vicinities of the Main Crater and the Daang Kastila fissure, must remain strictly prohibited.
Local government units are advised to continuously assess previously evacuated barangays around Taal Lake for damages and road accessibilities and to strengthen preparedness, contingency, and communication measures in case of renewed unrest. Residents of these barangays are advised to be always prepared, to keep calm and listen to information only from trusted or verified sources.
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. DOST-PHIVOLCS is closely monitoring Taal Volcano’s activity and any new significant development will be immediately communicated to all stakeholders.