By Marlon Atun
LEGAZPI CITY, Philippines — The Philippine Institute of Volcanology and Seismology (Phivolcs) has maintained Mayon Volcano at Alert Level 3, as recent decreases in volcanic activity are insufficient for a downgrade.
Dr. Paul Karson Alanis, senior science research specialist of Phivolcs, said that despite observing a downward trend over the past two weeks, most monitored parameters still meet Alert Level 3 conditions.
“As of July 29, the volcano is still effectively at ‘Day 0’ in terms of meeting the requirement for a sustained decline,” Alanis explained, referring to the agency’s protocol requiring at least two consecutive weeks of consistent decrease in key parameters before lowering the alert level.
Phivolcs noted that earlier increases in seismic activity—particularly volcano-tectonic earthquakes recorded in Sto. Domingo and Bacacay, Albay—contributed to heightened unrest, including episodes of strombolian activity, lava fountaining, intensified rockfalls, and elevated sulfur dioxide (SO₂) emissions.
At its peak, SO₂ emissions reached approximately 13,128 tonnes per day, the highest recorded in the past 26 years.
In recent days, however, volcanic activity has shown signs of easing, including reduced seismicity and the absence of the rumbling sounds previously heard within several kilometers of the crater.
Alanis clarified that these sounds were associated with strombolian eruptions—named after Italy’s Stromboli Volcano—which produce cannon-like bursts, as well as increased rockfall events.
Despite these improvements, Phivolcs emphasized that alert level downgrading is not automatic.
The agency continues to implement a “stand-down” procedure, which carefully evaluates multiple parameters such as sulfur dioxide emissions, ground deformation, volcanic earthquakes, rockfall events, pyroclastic density currents (PDCs), plume activity, lava fountaining, and ongoing lava effusion.
“While we are seeing a declining trend, it is not yet sufficient to justify lowering the alert level,” Alanis said.
Since the onset of the current eruption, Mayon has produced an estimated 88 million cubic meters of volcanic materials, including lava, ash, gases, and pyroclastic flows.
These deposits remain on the upper slopes and pose significant hazards, particularly within the 6-kilometer permanent danger zone (PDZ).
Phivolcs warned that these materials are unstable and highly erodible. Even without active eruptions, they may collapse and generate PDCs and ash clouds.
Additionally, loose and still-hot volcanic debris may trigger dangerous lahars during heavy rainfall, threatening communities along river channels.
As of July 29, Phivolcs recorded four volcanic earthquakes, 10 rockfall events, two PDCs, and sulfur dioxide emissions of 1,318 tonnes per day.
Authorities continue to urge the public to strictly avoid entry into the 6-km PDZ and to remain vigilant against secondary hazards such as ashfall and lahars as Mayon remains under Alert Level 3. (PIA Bicol)
