LEGAZPI CITY, Aug. 18 -- The sulfur dioxide (SO2) emission of Mayon Volcano surged to 8,393 tons per day on Aug. 17, prompting the Philippine Institute of Volcanology and Seismology (Phivolcs) to warn of possible renewed eruptive unrest.

In a bulletin on Tuesday, Phivolcs recorded seven volcanic earthquakes. Crater glow was faint but visible to the naked eye, while the plume was obscured.

Lava continued to flow through different gullies on Basud (3.8 km), Bonga (3.2 km), and Mi-sis (2.7 km).

In an advisory issued at 10:30 p.m. Monday, Phivolcs said the latest SO2 reading was based on averaged measurements from campaign ultraviolet spectrometry.

The latest reading was the highest recorded since volcanic gas concentrations began declin...