Mayon ash, side‑vent rumours denied

A volcano can throw ash into the sky without opening a new hole in its side, and that is exactly the point Philippine volcanologists spent April 10 trying to get across about Mayon. The rumor said a new side vent had opened; the official answer was no. (bomboradyo.com) The immediate trigger was an ash advisory on April 9 from the Tokyo Volcanic Ash Advisory Center, which tracks airborne ash for aviation. That notice said Mayon erupted at 08:50 Coordinated Universal Time and sent ash to flight level 090, about 9,000 feet, drifting north. (volcanodiscovery.com) That kind of notice is aimed first at pilots, because volcanic ash is not like campfire smoke. It is made of tiny rock and glass fragments that can sandblast aircraft surfaces and damage jet engines, which is why ash height and drift direction get reported in aviation language. (ospo.noaa.gov) Mayon is the kind of volcano where people are primed to believe dramatic new developments fast. National Aeronautics and Space Administration scientists describe it as the most active volcano in the Philippines, with 65 eruptions in the last 5,000 years and a new eruptive episode that began in January 2026. (science.nasa.gov) This eruption has already been busy enough without a side vent. On April 7, the Philippine Institute of Volcanology and Seismology recorded short-lived lava fountaining at the summit crater, with ash clouds rising 300 meters and drifting west-northwest while Alert Level 3 stayed in force. (gmanetwork.com) A side vent is a new opening on a volcano’s flank, like water suddenly punching through the side of a pipe instead of coming out the top. Doreen Abelinde of the Mayon Volcano Observatory said that is not what happened here, and said lava was still coming only from the crater. (bomboradyo.com) Her explanation was much less cinematic and much more normal for an ongoing eruption. She said the visible plume came from the Bonga gully after a pyroclastic density current formed when part of the flowing lava collapsed. (bomboradyo.com) A pyroclastic density current is a fast ground-hugging surge of hot ash, gas, and rock fragments, more like an avalanche than a chimney plume. When lava advances, cools, and cracks, pieces can break off and rush downslope, kicking up ash that looks dramatic from a distance and can be mistaken for a new vent. (bomboradyo.com) That distinction matters on Mayon because the hazard map is built around where material is actually coming from and how it moves. Under Alert Level 3, Philippine authorities have kept the six-kilometer permanent danger zone closed because pyroclastic flows, rockfalls, and lava can still race down gullies from the summit. (science.nasa.gov; gmanetwork.com) So the April 9 and April 10 story was really two different hazards unfolding at once. One was real ash high enough to trigger an aviation advisory, and the other was a false claim that the volcano had shifted into a different eruption pattern by opening a new side vent. (volcanodiscovery.com; bomboradyo.com)