This serves as a notice for the lowering of Taal Volcano’s status from Alert Level 3 (Magmatic Unrest) to Alert Level 2 (Decreased Unrest).
Following the phreatomagmatic eruption of the Main Crater on 26 March 2022 and six (6) weak phreatomagmatic bursts until 31 March 2022, unrest at Taal Volcano has markedly declined. Activity in the past two weeks has been characterized by a significant drop in volcanic degassing from the Main Crater and in the incidence of volcanic earthquakes. The decline in unrest is supported by the following observations:
1. Since the 26 March 2022 eruption, only 86 small-magnitude and imperceptible volcanic earthquakes have been recorded by the Taal Volcano Network (TVN). These consist of 26 volcanic tremors, 59 low-frequency volcanic earthquakes, and 1 volcano-tectonic event, most of which occurred 0-7 kilometers beneath the Main Crater and the eastern sector of Taal Volcano Island or TVI. Most earthquakes were generated by volcanic degassing from the shallow magma and hydrothermal region beneath the TVI edifice. In addition, background tremor associated with shallow hydrothermal activity ceased on 31 March. There has been no recorded seismic activity related to new magmatic intrusions from Taal’s deeper magma source since unrest began last year.
2. After sulfur dioxide or SO2 gas flux elevated in the first three weeks of March 2022 and peaked at 21,211 tonnes/day on 16 March, emissions suddenly dropped on 3 April 2022. SO2 flux since then has averaged 240 tonnes/day, decreasing to 103 tonnes/day yesterday, 8 April, the lowest flux recorded since unrest began in 2021. The rise in SO2 emissions prior to the 26 March phreatomagmatic eruption and its subsequent drop indicate that accumulated volcanic gas drives this type of eruptive activity at the Main Crater. Recent volcanic gas emissions, therefore, suggest that the potential for eruptive activity at present is low.
3. Ground deformation parameters for the period January 2021 to April 2022 from electronic tilt monitoring on TVI and continuous Global Positioning System (GPS) and InSAR analysis of Sentinel-1 satellite data over Taal Caldera indicated a general deflation of Taal centered on eastern TVI. GPS data further recorded deflation of TVI by as much as 11 centimeters on the southeastern flank. These parameters are all broadly consistent with depressurization of the hydrothermal region beneath TVI due to continuous degassing and gas release by phreatomagmatic activity at the Main Crater.
4. Activity in the Main Crater in the past week has been characterized by occasional weak plumes and longer periods of absence thereof, consistent with the significant decrease in magmatic degassing.
In view of the above observations, DOST-PHIVOLCS is lowering the alert status of Taal Volcano from Alert Level 3 to Alert Level 2 to reflect the overall decreasing trend in the level of monitoring parameters. Alert Level 2 means that there is decreased unrest but should not be interpreted that unrest has ceased or that the threat of an eruption has disappeared. Should an uptrend or pronounced change in monitored parameters occur, the Alert Level may be raised back to Alert Level 3. At such time, people residing within areas at high risk to base surges who have returned after the step-down to Alert Level 2 must therefore be prepared for a quick and organized evacuation. Conversely, should there be a persistent downtrend in monitored parameters after a sufficient observation period, the Alert Level will be further lowered to Alert Level 1.
DOST-PHIVOLCS reminds the public that at Alert Level 2, sudden steam-driven or phreatic explosions, volcanic earthquakes, ashfall and lethal accumulations or bursts of volcanic gas can occur and threaten areas within TVI and along its coast. Entry into TVI, Taal’s Permanent Danger Zone, must therefore be strictly prohibited. Local government units are advised to continually strengthen preparedness, contingency and communication measures especially for previously evacuated high-risk barangays in case of renewed unrest. 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 aircrafts. DOST-PHIVOLCS is closely monitoring Taal Volcano’s activity and any new significant development will be immediately communicated to all stakeholders.
DOST-PHIVOLCS
