Nineteen “very weak” phreatomagmatic bursts were recorded at Taal Volcano between 8:50 a.m. and 1:30 p.m. on Friday, Oct. 21, according to the Philippine Institute of Volcanology and Seismology (Phivolcs).
In an advisory issued at 2 p.m., Phivolcs said the phreatomagmatic bursts, which were detected by remote camera monitoring of Taal Main Crater, originated from a vent on the northeastern side of Taal Volcano.
Phreatomagmatic burst occurs when hot magma comes into contact with groundwater.
“Some of these events produced 200-meter-tall steam-rich plumes with a few emanating from very short dark ash plumes that immediately collapsed into the Main Crater Lake (MCL),” Phivolcs said.
“Many of the bursts were obscured by ongoing upwelling of hot volcanic gas in the MCL, while all events did not generate detectable signals in the seismic and infrasound records,” it added.
According to Phivolcs, Taal Volcano released an average of 6,702 tons per day of sulfur dioxide (SO2) when it was last measured on Oct. 20.
Phivolcs said Taal Volcano remains under Alert Level 1, which means it is “still in an abnormal condition and should not be interpreted to have ceased unrest nor ceased the threat of eruptive activity.”
“Should current phreatomagmatic activity worsen or pronounced changes in monitored parameters forewarn of increasing unrest, the alert level may be raised to Alert Level 2,” it said.
“At Alert Level 1, sudden steam-driven or phreatic explosions, volcanic earthquakes, minor ashfall and lethal accumulations or expulsions of volcanic gas can occur and threaten areas within TVI (Taal Volcano Island),” it added.
Phivolcs “strongly” recommended that entry into TVI—Taal’s permanent danger zone, especially the vicinities of the main crater and the Daang Kastila fissure, should be strictly prohibited.