THE Philippine Institute of Volcanology and Seismology (Phivolcs) warned the public against going into the vicinities of Mount Pinatubo in Zambales following a “weak explosion” recorded around noon Tuesday, November 30.

Phivolcs, in an advisory issued around 4 p.m. Tuesday, said the Pinatubo Volcano Network recorded “seismic and infrasound signals” of a weak explosion at the volcano between 12:09 p.m. and 12:13 p.m.

It said the weak explosion produced a plume, which was detected by the Himawari-8 Satellite and reported to the agency by the Tokyo Volcanic Ash Advisory Center.

“The seismic and infrasound signals are not typical of known volcanic processes and are currently being evaluated together with other potential sources, e.g. aircraft activity, ordnance disposal, and others,” said Phivolcs.

It added that there has been very low seismic activity in the past days and geochemical survey of the Pinatubo Crater Lake this November 2021 yielded “low diffuse volcanic CO2 flux (257 tonnes/day),” discounting magmatic activity beneath the edifice.

Phivolcs advised local government units (LGUs) to prohibit entry into the Pinatubo crater until the source of Tuesday’s explosion has been determined.

It also reminded communities and LGUs surrounding Pinatubo to be always prepared for both earthquake and volcanic hazards and to review, prepare and strengthen their contingency, emergency and other disaster preparedness plans.

It assured the public that Phivolcs continues to strengthen its monitoring of Mount Pinatubo, adding any new development will be relayed to all concerned.

Mount Pinatubo erupted on June 15, 1991, killing more than 840 people. It has been considered the world's largest volcanic eruption to happen in the past 100 years, said the USGS. (SunStar Philippines)