The Philippine Institute of Volcanology and Seismology on Wednesday said that while Taal volcano is having a "generally weaker eruption" at the main crater, the fissuring of areas around it shows that it is very much active underneath.
"It’s the rising of the magma that is causing the fissures,” said Phivolcs Director Renato Solidum during a press conference. “If the rise of magma is continuous, there is higher possibility of activity in Taal Volcano.”
Phivolcs earlier explained that fissures happen before an eruption as magma rises towards the volcano. This is followed by subsidence as the movement of magma creates empty space.
In its 8 a.m. bulletin on Wednesday, Phivolcs said it recorded 466 volcanic earthquakes since 1 p.m. on January 12. Of that number 156 were of Intensity I to IV.
“For volcanic earthquakes, that is strong,” said Phivolcs Volcano Monitoring and Eruption Prediction Division chief Bornas. “The earthquakes are also generated by the moving magma.”
Meanwhile, new fissures or cracks were observed in the villages of Sinisian, Mahabang Dahilig, Dayapan, Palanas, Sangalang, Poblacion, Mataas na Bayan in Lemery; Pansipit, Bilibinwang in Agoncillo; Poblacion 1, Poblacion 2, Poblacion 3, Poblacion 5 in Talisay; and Poblacion in San Nicolas.
Asked if the new fissures or cracks observed in Batangas were signs that a major or climactic explosion was fast approaching, Bornas said it would be hard to tell.
"It is better to observe the earthquakes,” Solidum said, although both earthquakes and fissures are indications of magma movement.
"If we observe harmonic tremors or continuous earthquakes then it should be close (to a major eruption),” he said.
Included in the bulletin was the level of sulfur dioxide emission at 1,686 tons/day as of Tuesday. This is much lower than the 5299 tons/day recorded on Monday, but still higher than usual.
"Even if the concentration went down…if it’s more than 500 tonnes per day then it’s still significant,” Solidum said.
He also said the sulfur dioxide is not a good gauge of whether an explosive eruption is happening soon since it’s possible that the vent was just blocked.
Phivolcs reminded the public that Alert Level 4 is still up, which means that a hazardous explosive eruption is still possible within days or hours. It reminded that there should be no people in the Taal Volcano Island and the high-risk areas within the 14-kilometer radius of the Taal main crater.