MT. PINATUBO, which last exploded in 1991 and affected many countries around the globe, is under close monitoring for signs of restiveness after an “explosion signal” was recorded on Tuesday, the Philippine Institute of Volcanology and Seismology said.
Authorities immediately banned any activity inside the crater of the volcano, which has become a popular site for adventure and nature tourism since its explosion re-drew the topography of several towns in Central Luzon.
Phivolcs reported that the Mt. Pinatubo Network recorded seismic and infrasound signals of a weak explosion around 12:09 p.m. and 12:13 p.m.
The event, according to a Phivolcs Bulletin issued at 4 p.m. revealed that the event produced a plume that was detected by the Himawari-8 Satellite and reported to DOST-Phivolcs 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, ordinance disposal, and others. In addition, 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,” the Phivolcs Pinatubo Volcano Advisory issued at 4 p.m. on November 30 stated.
“DOST-Phivolcs is cautioning the public to refrain from venturing in the vicinities of Pinatubo Volcano at this time,” it says.
Moreover, DOST-Phivolcs advised local government units to prohibit entry into Pinatubo Crater until the source of the explosion event has been determined.
DOST-Phivolcs also enjoined the LGUs to report any related information.
“Communities and local government units surrounding Pinatubo are reminded 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 said.
Meanwhile, the DOST-Phivolcs continues to strengthen its monitoring of the volcano with ongoing upgrades to the PVN or Pinatubo Volcano Network, periodic geochemical surveys of the Pinatubo Crater lake and GPS and satellite analysis of ground deformation.
In a radio interview, DOST Undersecretary Renato Solidum, the concurrent Director at Phivolcs, confirmed the explosion but said the explosion “was not typical” in explosions noted in other volcanoes.
It could be associated, he explained, “with aircraft activity or explosion of ordnance—so, besides volcanic activity, we are looking at other possibilities,” he said.
Nevertheless, he said any activity in Mt. Pinatubo is banned for now, although he noted that volcanic gas and earthquake activity are very low, “discounting any substantial” volcanic activity at the moment.
Solidum said the DOST-Phivolcs will try to examine satellite images available.
He recalled that at the end of the first quarter of 2021, an alert level was raised in Pinatubo because of quake activity, but there was no magma buildup.
“So far, there’s no report of ashfall anywhere,” he added.