Phivolcs confirms phreatic eruption at Pinatubo crater

Metro Manila (CNN Philippines, November 30)— The "weak explosion" at Mt. Pinatubo reported Tuesday afternoon has been confirmed as a phreatic or steam-driven explosion by the Philippine Institute of Volcanology and Seismology (Phivolcs).

"Based on visual reports of an eruption plume and seismic, infrasound and satellite detection, DOST-Phivolcs confirms that a phreatic eruption occurred at Pinatubo Crater between 12:09 and 12:13 p.m.," the agency said in an update posted on social media.

Phivolcs earlier said they were assessing the recorded explosion, which produced a plume, to determine its source. 

"Considering that there has been very low seismic activity in the volcano in the past days and low diffuse volcanic CO2 flux measured at Pinatubo Crater Lake, and high infrasound over seismic energy released by the eruption, the event was likely driven by shallow hydrothermal processes beneath the edifice," Phivolcs said.

There has been no report of ashfall from the event. But Phivolcs warned the public against going near Mt. Pinatubo, and urged local governments to prevent entry as "shallow phreatic or hydrothermal explosions such as the event of today can occur without warning."

Mt. Pinatubo last erupted in June 1991. It was one of the largest volcanic eruptions, according to the US Geological Survey, killing over 800 people.