An ash cloud over Mount St. Helens was not an eruption — high winds lifted old ash off the ground

A volcanic ash cloud rose to about 12,000 feet above sea level near Mount St. Helens on October 15, and the U.S. Geological Survey was blunt about it: “NO ERUPTION.” The Cascades Volcano Observatory attributed the cloud to “resuspended VA due to ground level high winds in the general vicinity of Mount St Helens,” meaning wind had picked up ash that was already lying on the ground.

Save more, waste less: The Cool Down’s newsletter sends smart, simple changes that help you and the planet in your everyday life.

Subscribe to The Cool Down →

We may earn a commission if you sign up.

The aviation color code never left green, and nothing inside the volcano changed that day. The episode is a reminder that a plume on a webcam and an eruption are two different things.

The October 15 notice led with NO ERUPTION

The observatory issued a Volcano Observatory Notice for Aviation at 20:01 UTC on October 15, Notice NR 2026/01, posted on the USGS volcano updates page. These notices are written for pilots and airline dispatchers, so they are terse. This one listed the aviation color code as green, unchanged from the previous notice, and gave the cloud height as 12,000 feet above mean sea level.

The source of the observation was a webcam, not an instrument on the mountain, and the cloud was moving northwest. The contacts on the notice were Tyler Paladino and the observatory’s duty scientist, which is routine for a VONA.

Local television reached the same conclusion the same day. KPTV’s headline read “No eruption at Mount St. Helens; winds stir old ash.”

Two scales are in play, and they are easy to confuse. The ground-based alert level, which the USGS lists as “normal” for Mount St. Helens, describes the volcano’s state of unrest. The aviation color code, green here, describes the hazard to aircraft. Both sat at their lowest settings through the whole episode, and the notice’s own wording explains why: with no eruption, the only ash in play was the old material wind had stirred.

How old ash ends up in the air again

Resuspension is the technical word for what happened. Ash that fell during earlier activity does not disappear; it sits on slopes, in drainages and on bare ground around the volcano. When strong, dry wind crosses that material, it can lift fine particles into a visible plume, and from a distance a webcam cannot tell that plume from a fresh emission.

That is why the notice labels the cloud as resuspended volcanic ash and spells out the cause. Aviation users need to know that ash is aloft, but they also need to know that no new magma or explosive activity is feeding it.

The event has precedent. KPTV carried a story in September 2025 about strong winds spreading dust and ash around the mountain, and AccuWeather has published an explainer that Mount St. Helens is not erupting again but stirring up leftover ash decades after 1980.

A week on, still green and still normal

The observatory’s weekly update on October 23, issued at 11:11 a.m. Pacific, put every Cascade Range volcano, Mount St. Helens included, at the “NORMAL” alert level and the green aviation color code. It noted that small earthquakes were detected at Mount St. Helens over the previous week,, and that routine gas flights measured normal background degassing.

Crews also installed sensors at Spirit Lake near the mountain that week. The same USGS profile of Mount St. Helens listed the volcano as green and normal as of 20:01 UTC on October 15, the moment of the notice itself.

The mountain is well watched. The USGS says the 1980-86 and 2004-2008 eruptions left Mount St. Helens with the best seismic monitoring network of any Cascade volcano, so a real change underground would be expected to show up in the instruments long before it appears on a camera.

The network has changed at the margins. The USGS profile records that the observatory dismantled its VALT seismic station on July 16, 2024, after 18 years of service, while the Spirit Lake sensors installed last week add to what the observatory can see. Neither change affects the October 15 reading, which came from a webcam and from the observatory’s duty scientist, not from a seismograph picking up magma movement.

The 1980 legacy that wind can still move

Mount St. Helens erupted on May 18, 1980, removing the upper 1,300 feet of the summit in a debris avalanche and leaving the horseshoe-shaped crater people see today, according to the USGS. Decades later, the surrounding landscape still holds loose volcanic material that wind can move.

What the sources do not say is how much ash was lifted on October 15 or how far it travelled. The notice gives a height and a direction, not a tonnage, and no official count of affected flights has been published.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

Save more, waste less: Subscribe to The Cool Down →

We may earn a commission if you sign up.