MANILA – The Philippine Institute of Volcanology and Seismology (Phivolcs) has raised the alert over Mayon Volcano to level 2.
In its latest bulletin, Phivolcs said "magma was intruding at depth and current conditions may eventually lead to a larger eruption."
Phivolcs said under alert level 2 (alarming), low to moderate level of seismic activity and episodic harmonic tremor are observed. Faint or intermittent crater glows and swelling of edifice may be detected.
The agency advised the public to avoid from entering the 6-kilometer-radius permanent danger zone (PDZ) of the Mayon ''to minimize risks from sudden explosions, rockfall and landslides."
Phivolcs said based on Mayon's behavior exhibited in recent eruptions, ''current observations may indicate the advent of quiet lava extrusion that may eventually lead to greater unrest."
Phivolcs said a visual observation of Mayon's summit crater last August 12 revealed a growth of a new lava dome approximately 30 to 50 meters high.
Phivolcs said the formation of the new lava dome was followed by ''very slight inflation or swelling of the middle slopes of the edifice'' since the volcano's phreatic eruption last May 7, 2013.
There were also ''significant increases in SO2 (sulfur dioxide) flux beyond the baseline level of 500 tons/day, based on campaign and continuous gas measurements for the past two months."
''Other monitored parameters such as the occurrence of volcanic earthquakes and rockfall, however, have remained at baseline levels, while almost no crater glow or 'banaag' has been detected in the last four months,'' Phivolcs said.
''The growth of the new summit dome, slight ground deformation and increased volcanic gas emission likely signify the slow intrusion and degassing of magma."