Mayon Volcano's sulfur emissions hit 26-year high, signaling potential for explosive eruption

LIGAO CITY, Albay — Mayon Volcano may be nearing a more explosive phase after sulfur dioxide (SO2) emissions reached its highest level in 26 years on Saturday, prompting state volcanologists to warn of possible changes in the volcano’s ongoing eruption. The Philippine Institute of Volcanology and Seismology (Phivolcs) said Mayon emitted an average of 13,128 metric tons of volcanic SO2 per day on Saturday, July 11, based on campaign ultraviolet spectrometry measurements. It said the emission was the highest recorded from the volcano in the past 26 years and only slightly lower than levels measured during Mayon’s explosive 2000 eruption. The elevated SO2 emissions, Phivolcs said, could indicate a change in eruptive behavior and “even lead to explosive eruption.” Such an eruption, it said, could generate larger and longer-traveling pyroclastic density currents on all sectors of the volcano, eject ballistic rock fragments from the summit crater, and produce more widespread ashfall, with impacts potentially worsened by prevailing poor weather conditions. The volcano has been erupting for 187 consecutive days while under Alert Level 3. Phivolcs said the sharp increase in SO2 emissions coincided with heightened volcanic activity, including 97 low-frequency volcanic earthquakes associated with volcanic degassing and minor Strombolian activity at the summit crater, and 304 rockfall events caused by collapses from new lava flows as of 8 p.m. It added that only slight inflation of the volcanic edifice and a modest increase in overall seismic energy had been observed, remaining consistent with the effusive eruption that has characterized Mayon since the start of its 2026 unrest.