Alaska’s Shishaldin volcano is still venting steam under an active unrest advisory

The Alaska Volcano Observatory’s daily update for September 16, 2026 listed Shishaldin Volcano at ADVISORY, aviation color code YELLOW, describing low-level seismic unrest that has continued for weeks without escalating. Clear satellite and webcam images that day showed steam still rising from the summit crater of the volcano, a nearly symmetrical cone rising 9,373 feet above Unimak Island in the eastern Aleutians. The observatory kept issuing daily updates on the volcano through the following week, into the current-as-of date of September 20, with nothing in the sequence of notice records suggesting the advisory had been lifted.

Shishaldin sits roughly 680 miles southwest of Anchorage, one of more than fifty historically active volcanoes the Alaska Volcano Observatory tracks across the Aleutian arc. The observatory itself is a joint effort of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys, a structure built specifically because no single agency could staff round-the-clock monitoring of a volcanic chain this remote on its own.

The September Update’s Specific Findings

The specific readings behind the advisory were modest: minor seismic activity, occasional infrasound signals consistent with small explosions deep in the volcano’s conduit, and the steam plumes visible in clear-weather webcam images. None of those signals, individually or together, met the threshold the observatory uses to raise the alert level further. Steam alone, in the observatory’s own framing, typically points to snow, ice, or groundwater being heated near the surface rather than to magma pushing upward, which is part of why the advisory stopped short of a higher tier.

Shishaldin has earned that close attention. Observatory records credit it with dozens of recorded episodes of unrest and roughly two dozen confirmed eruptions since 1775, including a 2019-2020 eruption that sent lava flowing outside the crater for the first time since 1976, and a more violent 2023 eruption whose largest explosion drove an ash cloud several miles into the sky. Measured against that history, the current advisory describes the volcano at its quietest, not its most threatening.

Reading an Alert Level Most People Have Never Heard Of

ADVISORY sits in the middle of a four-tier scale the observatory uses for every volcano it monitors, running from NORMAL and GREEN at the quiet end up through WATCH and ORANGE to WARNING and RED at the top. ADVISORY, paired with the YELLOW aviation code, signals a volcano that has woken up from background activity but is not currently erupting or considered imminently likely to.

The distinction carries real weight for pilots as much as for residents. Aviation color codes exist primarily to warn aircraft away from ash, and YELLOW tells flight crews that Shishaldin bears watching without requiring the rerouting a RED code would demand. The Aleutian arc sits directly beneath some of the busiest transpacific air routes connecting North America to Asia, which is part of why the observatory issues a fresh assessment of every monitored volcano along the chain each day rather than waiting for a change in conditions to prompt one.

Great Sitkin’s ongoing eruption is a useful example of how long a single alert level can hold once conditions stabilize. It has sat at WATCH for years without escalating to WARNING, because slow-moving lava confined to a summit crater poses a very different hazard to aviation than an explosive ash-producing event does, even though both would technically count as an eruption in progress.

A Volcano Wired With Sensors on a Remote Aleutian Island

Watching an unpopulated volcano on a sparsely inhabited island depends entirely on remote instruments. Shishaldin is monitored using local seismic and infrasound sensors, a telemetered geodetic network that tracks ground deformation, and web cameras that capture conditions whenever weather allows a clear view.

Beyond that local network, the observatory layers in regional infrasound arrays, lightning-detection data that can flag ash plumes even through cloud cover, and satellite imagery capable of picking up heat signatures or sulfur dioxide emissions the ground sensors might miss. It is that combination of instruments, not any single sensor, that let the September 16 update state with confidence that the unrest remained low-level.

A Milder Alert Than Its Neighbor Down the Chain

The same bulletin that reported on Shishaldin also covered Great Sitkin, a volcano roughly 300 miles to the northeast that has been actively erupting lava into its summit crater since July 2021, with no explosions there since an event in May of that year. Great Sitkin sat at WATCH, aviation code ORANGE, a full step above Shishaldin’s ADVISORY status, even though its own webcam images that day showed no unusual activity beyond the slow lava advance already underway.

The side-by-side listing is a reminder that Alaska’s alert levels track actual observed behavior rather than a fixed sense of which volcanoes are inherently more dangerous. Shishaldin has not erupted in this unrest episode; Great Sitkin has been erupting continuously for years. Matt Haney, the observatory’s Scientist-in-Charge, and Ronni Grapenthin, its acting coordinating scientist, oversee both assessments and update them daily as the underlying data changes, with Shishaldin’s steam plumes so far remaining exactly that: steam, not lava.

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

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