Brace for the “worst case scenario” on Taal Volcano in Batangas, according to the National Disaster Risk Reduction and Management Council, which said it was expecting it after a series of minor explosions on Thursday.
Under the worst case scenario, 500,000 residents would be affected by a major eruption.
NDRRMC executive director Ricardo Jalad said: “The worst case scenario is a violent eruption so many of our people would be affected.”
If Alert Level 4 is raised, those within the 14-kilometer danger zone should be evacuated, he said.
NDRRMC said amid the coronavirus pandemic, the evacuation of thousands of evacuees is a big challenge in the Calabarzon area.
“We need more evacuation centers,” Jalad said. “We really need to be prepared. We will use schools, mostly. The unoccupied housing projects of the National Housing Authority, too.”
Meanwhile, the Philippine Institute of Volcanology and Seismology (Phivolcs) said Taal Volcano had generated six phreatomagmatic bursts and 60 volcanic earthquakes in the past 24 hours.
In its latest bulletin Thursday, Phivolcs said the last phreatomagmatic burst was observed at 9:41 p.m. Wednesday, producing a short, jetted plume up to 700 meters high.
Phivolcs’ earlier data showed phreatomagmatic explosions were recorded at 5:18 a.m., 8:46 a.m., 9:15 a.m., 9:26 a.m., and 11:56 a.m. These phreatomagmatic eruptions lasted from one to seven minutes.
“Phreatomagmatic eruptions are caused by the interaction of magma and water. Eruptions normally consist of multiple explosive events, the interval of which may vary,” Phivolcs director Renato Solidum Jr. said.
He added that small phreatomagmatic eruption, together with the continued emission of high amounts of sulfur dioxide (SO2) and the increasing number of earthquakes indicate a continued magmatic activity that may lead to larger explosions or phreatomagmatic eruptions.
Sixty volcanic quakes were caused by movements or eruptions of magma from the volcano. The figure includes five explosion-type earthquakes, 24 low-frequency volcanic earthquakes, 21 volcanic tremor events having durations of two to four minutes, 10 hybrid earthquakes, and low-level background tremors that eased at 06:21 p.m. but resumed at 09:52 p.m.
Hybrid earthquakes indicate rock fracturing and magma or fluid movement.
High levels of SO2 gas emissions averaging at 11,397 tonnes/day, and steam-rich plumes that rose 1,500 meters high were also recorded.
Taal Volcano has been under Alert Level 3 (magmatic unrest) since July 1 after Phivolcs recorded a short-lived dark phreatomagmatic plume 1 kilometer-high in the afternoon.
Phivolcs reminded the public that under this level, magma extruding from the main crater could drive an explosive eruption.
Entry into Taal Volcano Island and into the high-risk barangays of Agoncillo and Laurel must be prohibited due to the hazards of pyroclastic density currents and volcanic tsunami should strong eruptions occur, it said.
Last July 1, Phivolcs recommended complete evacuation from the island, Taal Lake, Agoncillo, Batangas (Banyaga, Bilibinwang), and Laurel, Batangas (Gulod, Boso-Boso, Lakeshore Bugaan East).