Lava keeps creeping inside Great Sitkin’s summit crater under an orange aviation alert

Great Sitkin, a 5,708-foot volcano in Alaska’s central Aleutians, was still erupting lava inside its summit crater on September 30, 2026, and it remained at alert level WATCH with an aviation colour code of ORANGE. The Alaska Volcano Observatory posted the status in its daily multi-volcano update that afternoon, with Scientist-in-Charge Matt Haney of the U.S. Geological Survey listed as the contact.

The notice describes an eruption that has changed very little in character for years: lava oozing out slowly, no explosions, and a monitoring network that mostly records quiet.

A slow eruption now in its fifth year

The September 30 observatory update repeats language that has barely shifted for months. Lava is erupting slowly within the summit crater, it has filled most of the crater and spilled into valleys on the flanks, and no explosive event has occurred since May 2021. Observers had little new to add from the sky that day, because the notice records that clouds obscured both satellite and webcam images, leaving the seismic and infrasound sensors to carry the monitoring. Those instruments registered only minor seismic activity.

The effusion began in July 2021, after a Vulcanian explosion on May 25 of that year, according to the observatory’s volcano profile. AVO’s own account compares the sequence to the volcano’s 1974 activity, when an explosive start was likewise followed by lava extrusion. Great Sitkin sits in the Andreanof Islands, 26 miles from the community of Adak and 81 miles from Atka, roughly 1,167 miles southwest of Anchorage.

WATCH and ORANGE: one condition, two audiences

The two labels describe the same condition for two audiences. WATCH is the ground-level alert level: a volcano is erupting, or hazardous activity is under way, with the potential for a more serious escalation. ORANGE is the aviation colour code, which signals to pilots and dispatchers that an eruption is under way or that ash emission is possible and unconfirmed. Great Sitkin has carried both designations since the lava began to emerge in 2021, a stretch of more than four years without a downgrade. For airlines flying the North Pacific routes that pass near the Aleutians, that steady ORANGE is a standing instruction to treat the volcano as capable of sending ash aloft with little notice, even though the eruption has not produced any since the 2021 explosion.

The reason the level has not dropped is that the lava has never stopped moving. Effusive eruptions of this kind build domes and flows rather than ash columns, but a growing dome on a steep, glacier-capped summit can collapse or shed material, and the observatory keeps the higher designation until the supply of fresh lava ends.

Month-by-month evidence of a dome still growing

Earlier notices show the lava did not simply sit still. In a May 10 update, monitoring equipment picked up rockfall signals from the expanding lava dome, even though cloud cover again blocked a clear view. A June 26 notice reported dome growth toward the east-southeast on June 22, visible in satellite radar, along with slightly elevated surface temperatures whenever weather allowed a look. Webcams that day showed no visible activity.

The September 16 update read, in the observatory’s words: “Slow eruption of lava within the summit crater continues, accompanied by weak seismicity.” Minor earthquakes had occurred over the previous day, and clear webcam views showed no concerning changes to the active dome. Two weeks later, the September 30 update said essentially the same thing.

Seismic and infrasound sensors when the clouds close in

AVO is a partnership of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute and the State of Alaska, and the daily update is the format it uses to cover every Alaskan volcano under watch at once. For Great Sitkin the toolkit named in the notices is local seismic, geodetic and infrasound sensors, satellite imagery, web cameras and regional networks. Each has a blind spot, and the observatory’s updates say so plainly when a channel goes dark. Satellites and webcams fail under the heavy cloud that is routine in the Aleutians, which is why the seismic and infrasound channels matter on days like September 30.

The same notice also carried a second Aleutian entry. Shishaldin was listed at ADVISORY with a YELLOW aviation code, with low-level unrest continuing and slightly elevated seismic and infrasound activity, a lower tier than Great Sitkin’s.

The designation will change only when the observatory’s scientists see the lava supply end or the behaviour of the dome shift. As of the Alaska Volcano Observatory’s September 30 update, which lists Matt Haney as scientist-in-charge, neither has happened: Great Sitkin remains at WATCH and ORANGE, with lava still creeping inside its crater and the observatory’s daily updates continuing to track it.

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

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