The Philippine Institute of Volcanology and Seismology (Phivolcs) on Tuesday said the cracks emerging in roads in Batangas are signs that magma or molten rock is moving toward Taal volcano.
“Ito nao-observe natin na tuloy-tuloy na paglindol na malalaki kasama na ’yung fissuring ay naghuhudyat na meron talagang magma na umaakyat pa sa Taal,” Mariton Bornas, chief of the Phivolcs’ volcano monitoring and eruption prediction division, told media.
(What we are observing now — the earthquakes and the fissures — are signs that magma is still rising in Taal.)
At least 335 volcanic earthquakes were monitored between Sunday and to Tuesday 10 a.m. in the area. The strongest was a magnitude 4.1.
“For volcanic earthquakes, this is strong,” Bornas said.
Taal volcano was first placed on Alert Level 1 in March 2019 after the Phivolcs monitored a substantial number of weak earthquakes in the area. Earthquake swarms are usually monitored before a volcanic eruption.
Meanwhile, fractures on the ground were seen in various parts of Batangas, including the towns of Agoncillo, Lemery, San Nicolas and Talisay, destroying some houses.
Bornas, who has been closely studying Taal, said that during past eruptions fissures appeared before a major or explosive eruption.
“Fissures appear and then the ground sinks after a large eruption,” Bornas said, adding that the drop is caused by the vacuum created underground when the volcano discharges magma to the surface.
However, Bornas clarified that magma cannot flow from the fissures. “These are ground deformation features,” she said.
It is unclear if the fissures will bring about an explosive eruption in a few days, but Bornas said it is similar to what happened in 1911.
Bornas, who recently published a journal paper with other experts on the history of Taal, recalled how historical accounts recorded the 1911 explosion as starting out with low level activity in the main crater on January 27, followed by the appearance of fissures on January 28. It was on January 30 that the big eruption happened.
It is also notable that the fissures in 1911 happened in the same areas in Batangas: Lemery, San Nicolas, Taal, Talisay and Tanauan.
Asked if this meant that the residents should leave areas that showed signs of fissures, Bornas said, “I think they should have already evacuated. We would like to reiterate the enforcement of evacuation.”
Communities around the 14-kilometer zone of Taal volcano should have been evacuated, based on the advice of the Phivolcs.
Bornas also clarified that the presence of fissures cannot predict an explosive eruption; only that it is an indication there is a large volume of magma movement.
She said the danger now is that while there is low surface activity in the volcano, the passage to the surface has already been cleared after hours of phreatic explosions during the first day.
“Taal has been opened up. If there is magma coming from beneath, it will be able to quickly ascend. There are no more blockages,” she said.
During the press conferences, journalists asked for other effects of the eruption, including reports that parts of the lake have turned green.
Bornas said that while it is hard to evaluate such reports since experts have not seen it, there have been accounts during the 1911 eruption about one of the smaller lakes inside the Taal caldera turning green.
“They called it laguna verde. The water turned green because of the high sulfur content,” she said, adding that sulfur oxide only appears when magma has almost reached the surface.
She assured the public that the Phivolcs is continuously monitoring the volcano. At the same time, she reiterated that at Alert Level 4, people should understand that an explosive eruption can happen any time.