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MANILA, Philippines (UPDATED) – The Philippine Institute of Volcanology and Seismology (Phivolcs) downgraded Taal Volcano in Batangas from Alert Level 3 to Alert Level 2 on Friday, February 14.
“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,” said Phivolcs.
At this point, if volcanic activity continues to ease for a “sufficient observation period,” then Taal could be further lowered to Alert Level 1. But if volcanic activity escalates, the volcano could be returned to Alert Level 3.
What were the reasons for the downgrade? Phivolcs explained that Taal’s condition in the past 3 weeks was characterized by the factors below.
Less frequent volcanic earthquake activity: Since January 26, volcanic earthquakes recorded by the Taal Volcano Network have averaged 141 per day. The number of “significant events” recorded by the Philippine Seismic Network across the Taal region also declined to 127, with magnitudes 1.4 to 4.3. “The number and energy of tremor and low-frequency events associated with activity in the shallow magma and hydrothermal region…have also diminished.”
Stabilizing ground deformation of the Taal Caldera and Taal Volcano Island edifices: Data from January 13 to February 11 showed “net subsidence” or downward settling of the Taal Caldera and Taal Volcano Island, after the inflation of the northwestern caldera and the subsidence of the island from January 12 to 13. There has been “relaxation” of the volcano’s edifice after the movement of magma stopped.
Weak steam and gas emissions at the main crater: Sulfur dioxide (SO2), a major gas component of magma, has averaged only 62 tons per day since January 26. The weak steam-laden plumes seen at the main crater are also “consistent with decreased magmatic unrest.”
What happens under Alert Level 2? Phivolcs warned that the following may still occur and threaten Taal Volcano Island:
- sudden steam-driven or phreatic explosions
- volcanic earthquakes
- lethal accumulations or expulsions of volcanic gas
What should the public do? Phivolcs again recommended that entry into Taal Volcano Island, classified as a Permanent Danger Zone, remain strictly prohibited.
When Taal was under Alert Level 3, these areas had been included in the 7-kilometer radius that was off-limits:
- barangays of Bilibinwang, Subic Ilaya, and Banyaga in Agoncillo
- barangays of Gulod, Buso-Buso, and Bugaan East in Laurel
On Friday, Phivolcs said, “Local government units are advised to additionally assess previously evacuated areas within the 7-kilometer radius for damage and road accessibilities and to strengthen preparedness, contingency, and communication measures in case of renewed unrest.”
The unrest has affected 151,242 families or 565,715 persons in Batangas, Quezon, Laguna, and Cavite as of Friday.
Shortly before Phivolcs announced the downgrade to Alert Level 2, there were 3,002 families or 11,013 persons staying in evacuation centers. At the height of the unrest when a 14-kilometer-radius danger zone was enforced, there were over 38,000 families in evacuation centers. – Rappler.com