The possibility of a widespread eruption in the Taal Caldera has been dismissed by the Philippine Institute of Volcanology and Seismology (PHIVOLCS).
"Ang Taal Volcano po ay hindi lamang 'yung pulo, kasama rito 'yung malaking caldera na kinabibilangan po ng mga dalisdis sa harap ng Tagaytay, sa paligid ng bulkan," Mariton Bornas, PHIVOLCS Volcano Monitoring and Eruption Prediction Division chief, said at a press conference Friday.
"Ang typical po na repose ng caldera ay nasa hundreds of thousands of years... 'yung probabilities po na mag-activate sila ay napakaliit parang hindi po natin dapat ina-alarm ang ating mga kababayan na maaaring itong malaking caldera ang puputok," she said.
Data from PHIVOLCS show that the Taal Caldera measures 25 kilometers across and was formed between 140,000 to 5,380 BP (before present). Taal Lake is also within the said caldera.
In its 8 a.m. bulletin, PHIVOLCS said that the existing fissures in the towns of Lemery, Agoncillo, Talisay, and San Nicolas have widened by a few centimeters.
The said towns—along with Laurel, Sta. Teresita, Cuenca, Lipa, Mataasnakahoy, Balete, eastern part of Malvar, and some parts of Tanauan City—form part of the Taal Caldera, according to PHIVOLCS.
Bornas, however, underscored that Taal's records of activity for thousands of years showed that the eruptions take place mainly on the Taal Volcano island where 47 craters and four maars (low-relief, broad volcanic crater formed by shallow explosive eruptions) are located.
"Lahat po ng activity niya ay naka-concentrate dito po sa Taal Volcano island. Ito po 'yung active crater kaya po 'yung bulkan kung puputok po siya, ang kaniyang gagamitin na daanan ay 'yung established na, 'yung matagal na," she said.
"'Yung nakikita po nating parameters, hindi po siya nagsasaad ng isang malawakang pagputok ng Taal Caldera, wala po tayo sa ganoon," she added.
Receding waters in Taal Lake
Bornas, however, said that Taal Lake is not likely to be drained in case the expected hazardous eruption occur.
"Ang lawa po ay basin at ang basin po ay pini-feed ng groundwater system—'yan po ay sa buong kalupaan sa paligid po ng lawa," she said.
"So kahit po mabawasan 'yun, mayroon at mayroong papasok diyan lalo na kung umuulan. So, eventually 'yung tubig sa paligid ay bababa naman po sa lawa," she added.
Alert Level 4 remains over Taal, five days after its initial eruption on Sunday.
Though "relative lull" has been observed in previous days, volcanologists warned that a hazardous eruption is still possible within hours to days. — RSJ, GMA News