The Alaska Volcano Observatory on Tuesday lowered the alert level for Kupreanof Volcano on the Alaska Peninsula after weeks of declining activity.

Kupreanof has not erupted in approximately 570,000 years. The observatory raised the alert level in May 2026 after detecting an increase in nearby earthquakes and elevated sulfur dioxide emissions associated with magma movement. Seismicity was first detected in February 2026 and increased over subsequent months, with earthquakes as large as magnitude 3.1 recorded. Sulfur dioxide emission rates reached roughly 100 to 1,000 tons per day beginning in early April, well above the background rate of less than 100 tons per day.

Since late August, the number of earthquakes has declined and sulfur dioxide emissions have returned to background levels. Intensity of steam emissions has also decreased. The Alaska Volcano Observatory stated that these changes indicate the magmatic intrusion beneath the volcano has stalled.

The Aviation Color Code and Volcano Alert Level have been changed from Yellow/Advisory to Unassigned. The observatory noted that the designation is Unassigned rather than Green/Normal due to insufficient coverage by ground-based monitoring instruments at the remote peak.

No eruption is indicated by current data. The volcano remains under observation by the Alaska Volcano Observatory.

SOURCES
Alaska Beacon: https://alaskabeacon.com/2026/09/08/remote-alaska-volcano-has-calmed-down-after-summertime-unrest-observers-say/

USGS/Alaska Volcano Observatory notice: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-AVO-2026-09-08T22:30:01+00:00