Reported Tuesday afternoon November 30, 2021, by the Philippine Institute of Volcanology and Seismology (Phivolcs) a “weak explosion” at Mt. Pinatubo has been confirmed as a phreatic or steam-driven explosion. Phivolcs earlier said they were assessing the recorded explosion, which produced a plume, to determine its source. The agency also said in an update posted on social media DOST-Phivolcs confirms that a phreatic eruption occurred at Pinatubo Crater between 12:09 and 12:13 p.m. based on visual reports of an eruption plume and seismic, infrasound and satellite detection.
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.” The event was likely driven by shallow hydrothermal processes beneath the edifice,” Phivolcs said. 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. According to the US Geological Survey, in June 1991 when Mt. Pinatubo last erupted; it was one of the largest volcanic eruptions, killing over 800 people.
