The Philippine Institute of Volcanology and Seismology (Phivolcs) first observed what is called lava fountaining from 2:49 am to 4:28 am on Monday, during a magmatic eruption.
"This magmatic eruption is characterized by weak lava fountaining accompanied by thunder and flashes of lightning," Phivolcs said in an 8 am bulletin.
Then there was a "brief waning of activity," but the "weak sporadic lava fountaining and hydrovolcanic activity at the main crater" resumed shortly after. This "generated steam-laden plumes" around two kilometers tall, said Phivolcs in a 4 pm update.
The agency also said "new lateral vents" opened up on the crater's northern flank, "where short 500-meter lava fountains emanate."
Monday's magmatic eruption came after a phreatic or steam-driven eruption "in several points" inside the Taal Volcano's main crater, which had begun at 1 pm on Sunday, January 12. An ash column 10 to 15 kilometers high was generated.
Alert Levels 2, 3, and then 4 were swiftly raised on Sunday. Alert Level 4 means a hazardous eruption is "imminent," or may occur "within hours to days." (READ: TIMELINE: Taal Volcano eruptions since 1572)
There have been a total of 144 volcanic earthquakes in the Taal area recorded since 1 pm on Sunday.
Phivolcs said 44 of these earthquakes were felt with intensities ranging from Intensity I to V in Tagaytay City; and in Alitagtag, Lemery, Santo Tomas, and Talisay in Batangas.
"Such intense seismic activity probably signifies continuous magma intrusion beneath the Taal edifice, which may lead to further eruptive activity," Phivolcs said.
Batangas was placed under a state of calamity on Monday. The number of evacuees rose to more than 24,000. (READ: 'Lubog na lahat': Calawit residents return to crushed homes)
This triggered suspensions of classes and government work for Monday and also for Tuesday, January 14. (READ: Stores run out of face masks as Taal Volcano ash spreads to Calabarzon, Metro Manila)
"Civil aviation authorities must advise aircraft to avoid the airspace around Taal Volcano as airborne ash and ballistic fragments from the eruption column pose hazards to aircraft," Phivolcs said. – Rappler.com