Legazpi city: The Philippine Institute of Volcanology and Seismology (Phivolcs) has recently downgraded the alert status of Mayon Volcano from Alert Level 3 to Alert Level 2, indicating a moderate level of unrest.
According to Philippines News Agency, this decision was based on the continuous monitoring and observation of the volcano's activity, which showed a general decline in unrest since July 23. The data were gathered through various monitored parameters, which indicated reduced eruptive activity at the summit crater. Notably, there has been a decrease in Strombolian events, lava effusion, and lava collapse-fed rockfall and pyroclastic density currents (PDCs).
The advance of active lava flows in the Mi-isi, Bonga, and Basud Gullies has halted at specific radial distances from the summit crater, signaling a pause in the magma supply. Additionally, the frequency of lava collapse-fed rockfall incidents has significantly decreased, from an average of 278 events per day at the start of the eruption to just 12 events per day from July 23. Strombolian and PDC activities have also ceased since the last recorded events in late July.
Phivolcs reported that the total volume of erupted lava, including rockfall and PDC deposits, is approximately 89 million cubic meters. Seismic activity has also reduced, with volcanic earthquakes diminishing from an average of 57 events per day to 13 events per day.
Real-time seismic energy release from the volcano has returned to pre-eruption levels, further confirming the decrease in surface activity and the cessation of magma supply to the summit crater. Volcanic sulfur gas (SO2) emissions have also decreased, with current levels still above baseline but averaging lower than the peak recorded in June.
Despite the downgraded alert status, Phivolcs emphasized that the volcano's unrest has not entirely ceased. The edifice remains pressurized, and SO2 emissions are still relatively high. The public is advised to avoid the 6-km-radius Permanent Danger Zone (PDZ) due to the risk of sudden minor explosions or phreatic eruptions, which could pose volcanic hazards such as short-range PDCs, rockfall, and ballistic projectiles.
Communities near lahar channels, especially those draining the Mi-isi, Bonga, and Basud Gullies, should remain vigilant and be prepared for potential evacuation during heavy or intense rainfall, which could trigger life-threatening lahars and sediment-laden streamflow. Civil aviation authorities are also advised to caution pilots against flying near the volcano's summit due to the potential hazards of ash from sudden eruptions.
