A massive volcano near Alaska’s largest city, Anchorage, that has been inactive for more than 100 years is showing signs of seismic activity according to scientists. Mt. Iliamna, a 10,016-foot volcano, sits approximately 130 miles away from Anchorage, posing a significant threat for eruption. On June 15, seismic activity ramped up from the normally dormant to a “nearly continuous” rate for several hours, a local observatory reported. As of July 2025, scientists reported an increase in vigorous seismic activity beneath Iliamna volcano, which had been dormant for over a century.
According to the Alaska Volcano Observatory (via NASA), the seismic tremors were significant enough to indicate renewed magma movement. Since its last true eruption in 1867, the volcano was recorded ejecting smoke and light ash in 1876, 1933, 1941 and 1947, according to the NPS. Further reports of smoke and light ash were reported in the winter of 1956 and early spring of 1957, but those reports were not confirmed, the NPS stated. In 1958, four columns of vapor were shooting out of vents on the eastern side of the volcano, according to the NPS. That was the last time smoke appeared to be ejected by the volcano. It was also noted that the quakes could result from an avalanche rather than an impending eruption.
While lava movement could very well be the reason for Illiamna’s recent activity, large scale avalanches may be the more likely culprit, according to the NPS. The slopes of Illiamna are covered in glaciers; snow and ice sit on a base of unstable Jurassic-era granite. Iliamna often experiences massive avalanches and slides due to the combination of glacial ice weakened rock and volcanic heat.
Although Iliamna is very remote, located deep within the Chigmit Mountains within Lake Clark National Park and Preserve, it is monitored closely be volcanologists due to its potential hazards. The Alaska Volcano Observatory monitors 51 other active volcanos within the state. This includes the Redoubt Volcano, Iliamna’s more eruptive neighbor, which is also located within the preserve. Redoubt last began erupting on March 22, 2009, and activity continued for several months. During the eruptions, reports found ash clouds reaching as high as 65,000 feet (20,000 meters) above sea level…