MANILA, Philippines — Mayon Volcano in Albay was observed producing a fast-moving avalanche of hot gas, ash, and fragmented volcanic rock—known as a lava-collapse pyroclastic density current (PDC), the Philippine Institute of Volcanology and Seismology (Phivolcs) said Friday. The lava-collapse PDC was ongoing as of Friday afternoon, Phivolcs wrote in a Facebook post. “PDCs are
