The Philippine Institute of Volcanology and Seismology (Phivolcs) has so far recorded four short phreatomagmatic bursts in the Taal Volcano since it was placed under Alert Level 3 (magmatic unrest).
In a bulletin Friday, Phivolcs said phreatomagmatic bursts happened at 6:26 p.m., 7:21 p.m., 7:41 p.m. and 8:20 p.m. on July 1.
Each of these lasted no longer than two minutes and produced short jetted plumes that rose 200 meters above the main crater lake.
The phreatomagmatic eruption, a result of the interaction between magma and water, occurred at the main crater at 3:16 p.m. Thursday, prompting Phivolcs to raise the volcano’s alert level status.
The eruption generated a dark grayish plume that rose 1,000 meters.
Phivolcs also recommended complete evacuation in some parts of Agoncillo and Laurel, Batangas, due to possible hazards of pyroclastic density currents and volcanic tsunami.
The evacuation was recommended in the Taal Volcano Island (TVI), Taal Lake, Agoncillo, Batangas (Banyaga, Bilibinwang), and Laurel, Batangas (Gulod, Boso-Boso, Lakeshore Bugaan East).
Meanwhile, for the past 24 hours, 21 volcanic earthquakes were recorded. These included one explosion-type earthquake, 22 low frequency volcanic earthquakes and two volcanic tremor events having durations of three minutes.
Volcanic quakes are caused by movements or eruptions of magma from the volcano. Volcanic quakes last less than a minute, while volcanic tremors last more than a minute, several minutes, hours, or even days.
Under Alert Level 3, magma extruding from the main crater could drive explosive eruption.
Phivolcs said the high level of sulfur dioxide (SO2) emission, which averaged 13,287 tonnes/day on July 1. On June 28, the SO2 emission averaged 14,326 tonnes/day – the highest ever recorded in Taal.
The high SO2 emission was the reason why volcanic smog (vog) was seen over the Taal Caldera, Phivolcs chief of volcano monitoring division Maria Antonia Bornas said.
Phivolcs reminded the public that the Taal Volcano Island is a permanent danger zone and entry into the island and high-risk barangays of Agoncillo and Laurel must be prohibited.
All activities on Taal Lake should not be allowed at this time, it added.
Communities around the Taal Lake shores are advised to remain vigilant and take precautionary measures against possible airborne ash and vog.