By Alexandria Dennise San Juan
State volcanologists continue to monitor Taal Volcano which remains on Alert Level 3 as volcanic threats persist, nearly a month after it erupted.
The Philippine Institute of Volcanology and Seismology (Phivolcs) said there is a “relatively high unrest manifested by seismic swarms including the increasing occurrence of low-frequency earthquakes and/or harmonic tremors where some events are felt.”
In its latest bulletin issued Saturday, Phivolcs said moderate emission of white to dirty white steam-laden plumes was observed in the Main Crater of Taal rising 200 to 300 meter high before drifting southwest.
The weak steaming, Phivolcs noted continues to come out from fissure vents along the Daang Kastila trail which has been used by tourists to see the Main Crater Lake from the view deck.
Sulfur dioxide (SO2) emission slightly increased and was measured at an average of 54 tons per day on Friday, February 7. SO2 levels had been very low and undetected in the past two days.
A higher level of SO2, which is a major gas component of magma, is being released when magma or molten rocks are near the surface of a volcano indicating a possible magmatic eruption.
Volcanic earthquakes also persist within Taal Volcano Island which signifies a continuous movement of magma underneath that could lead to eruptive activity at the Main Crater.
Phivolcs downgraded Taal’s danger status from Alert Level 4 to Alert Level 3 on January 26, two weeks after its phreatic (steam-driven) eruption on January 12 forcing thousands of residents to evacuate due to thick ash that blanketed their homes.
The agency reiterates its warning to the public that sudden steam-driven and even weak phreatomagmatic explosions, volcanic earthquakes, ashfall, and lethal volcanic gas expulsions can still occur and threaten areas within Taal Volcano Island and nearby lakeshore communities.
Phivolcs also maintained that entry to the volcano island as well as into areas in the Taal Lake and communities west of the island within a seven-kilometer radius from the Main Crater must be “strictly prohibited.”
“Local government units are advised to assess areas outside the seven-kilometer radius for damages and road accessibilities and to strengthen preparedness, contingency and communication measures in case of renewed unrest,” the agency added.
Communities beside active river channels particularly where ash from the main eruption phase has been thickly deposited should increase vigilance when there is heavy and prolonged rainfall since the ash can be washed away and form lahars along the channels.