Largest uson logged in Mayon - PHIVOLCS

The largest pyroclastic density current (PDC) or uson in Mayon Volcano was generated on Monday morning, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said. 

The ongoing PDC was first recorded at 10:35 a.m. and traveled down as far as 4 kilometer radial distance on the Mi-isi Gully. 

“The PDC generated an extensive 1 kilometer-tall brownish ash plume that drifted to the southwest and brought ashfall over several barangays of Camalig and Guinobatan, Albay,” said PHIVOLCS. 

Mayon Volcano remains under Alert Level 3 and entry into the 6-kilometer radius Permanent Danger Zone is strictly prohibited. 

According to PHIVOLCS, pyroclastics are fragmented volcanic particles. When these mix with hot gases and ash, they form what are known as PDCs.

State seismologists said PDCs can range from pyroclastic flows to pyroclastic surges. PDCs are generated when an eruption column collapses under its own weight. Unlike typical rockfalls, which involve only rocks, PDCs are more dangerous due to their combination of gases, ash, and rocks. —Vince Angelo Ferreras/RF, GMA Integrated News