MANILA (UPDATE) - A "crater glow" has been observed at the Mayon Volcano in Albay over the past two days, indicating that "remnant magma" from its last explosion may be rising to shallow levels, Phivolcs said Wednesday as it warned against entry into danger zones.
In a 4 p.m. advisory, Phivolcs said the glow has been detected at the summit crater "that is likely caused by hot magmatic gases heating the overlying atmosphere."
"This suggests the possibility that remnant magma may be quietly rising to the shallow levels of the edifice," it said.
It said it is "closely monitoring Mayon Volcano's condition."
Alert Level 2 remains at the volcano given its "moderate level of unrest," the state seismology agency said.
But it said entry should be prohibited in areas covered by the 6-kilometer radius permanent danger zone and the precautionary 7-km radius extended danger zone.
These areas span the volcano's "south-southwest to east-northeast sector" stretching from Barangay Anoling in Camalig town to Sta. Misericordia in Sto. Domingo town.
Mayon, Bicol's picturesque volcano known for its perfect cone, last erupted in 2018. Since then, it has shown "declining earthquake activity and sulfur dioxide emissions," but slight swelling on its edifice began in Feb. 2019.
But Phivolcs said such activity does not show a renewed magma rise but involves magma "already emplaced beneath the edifice."
Phivolcs reminded the public that "sudden explosions, lava collapse, pyroclastic density currents or PDCs and ashfall can occur without warning and threaten areas in the upper to middle slopes of Mayon."
"People residing close to these danger areas are also advised to observe precautions against rockfalls, PDCs and ashfall," it said.
Lahar-prone streams and rivers should also be avoided especially during extreme weather or heavy rainfall. Phivolcs also urged civil aviation authorities to warn pilots against flying near the volcano's summit to avoid exposure to possible sudden explosions.
Mayon's activity was observed just weeks since the ash-driven explosion of the Taal Volcano in Batangas, which caused ashfall around Batangas and nearby areas, prompting massive evacuations and causing billions worth of damage on crops and property.
After two weeks of implementing alert level 4, which warns of Taal's imminent eruption, Phivolcs lowered the alert level at the volcano on Jan. 26.