Taal quakes weaker but magma near surface: Phivolcs

Kristine Sabillo, ABS-CBN News

Posted at Jan 22 2020 11:22 AM | Updated as of Jan 22 2020 12:18 PM

Taal volcano emits steam-laden plumes from the main crater as seen from the municipality of Mataasnakahoy, Batangas on Tuesday afternoon. Phivolcs reiterated on January 22, the imposed total evacuation of the Taal Volcano Island and other high-risk areas within the 14-km radius of the main crater and along Pansipit river where fissuring has been observed. Gigie Cruz, ABS-CBN News

MANILA - The Philippine Institute of Volcanology and Seismology (Phivolcs) on Wednesday said it is hard for them to assess if Taal Volcano is safe because of the magma that has already reached near the surface.

“This is a dilemma kung paano natin iinterpret 'yung nakapondo na na magma na dumaan at nagbitak bitak na lupa,” said Phivolcs Volcano Monitoring and Eruption Prediction Division head Mariton Bornas.

(It’s a dilemma how we will interpret the magma that has risen and has caused fissures.)

She said this after explaining that the earthquakes detected in Taal Volcano was “significantly weaker,” at least since the first round of eruptions last January 12.

Fissures or cracks have appeared in several towns in Batangas last week, which Phivolcs said meant that magma was flowing underground. Bornas also said they will have to measure how much magma is now near the main crater and is ready to be expelled.

By Wednesday morning, Phivolcs reported weaker emissions of white steam-laden plumes at 50 to 500 meters high. This is low compared to the dark-colored ash plumes that towered over Taal by 1 kilometer or more during the first week of the eruption.

Sulfur dioxide emissions on Wednesday were also low at 153 tons a day.

Phivolcs’ Taal Volcano Network recorded 481 volcanic earthquakes in the last 24 hours including 8 low-frequency earthquakes, which have been linked to magma movement. Bornas said this is significantly lower compared to previous days.

“But this does not mean that we should be complacent,” Bornas said, adding that the lower sulfur dioxide might also just mean that the vents are temporarily blocked.

Sulfur dioxide separates from magma as it nears the surface. When the eruptions started, sulfur dioxide levels was at an average of around 5,000 tons per day. But it has fluctuated in the past days.


NOT ALL CAN RETURN

Bornas said that if the lower parameters continue for two weeks, they can lower the Alert Level from 4 to 3. 

“But not all can return (to their homes). We will not recommend that,” she said, explaining that when Mayon erupted, the people were not allowed to enter the permanent danger zone and the extended danger zone at a radius of 7 kilometers.

And even for those who will be allowed to return, they will have to be ready every day to evacuate in case of a strong eruption.

Phivolcs earlier said that the current eruption escalated quicker than usual, giving them only two hours from when earthquake swarms started until the volcano had steam-driven eruptions.

Besides no longer having water in its main crater, Bornas said aerial surveys showed that there were new features that have appeared.

“There is what we think is a new cone that has been created by lava fountaining events after the main (eruption) phase,” she said.

Bornas reiterated that Alert Level 4 is still up in Taal Volcano, meaning that a hazardous explosive eruption can happen within hours or days. Taal Volcano island remains off limits, as well as the high-risk areas in the 14-kilometer radius of the main crater. These are towns that are at risk in case base surges or blasts of hot gas, ash and volcanic material is generated by an exploding Taal Volcano.