Alaskan volcano rumbling despite being dormant for over 100 years, scientists say

An Alaskan volcano that has been inactive for more than 100 years is showing signs of rumbling, according to scientists.

However, there's a chance that the activity could be signs of a pending avalanche, rather than a volcanic eruption, NASA said.

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The Iliamna volcano, located near the Cook Inlet in southern Alaska, last erupted in 1867, but would still rumble every few years due to avalanches large enough to register on nearby seismic and infrasound instruments, according to NASA.

The region has recently experienced a "flurry of shaking," according to the Alaska Volcano Observatory.

NASA Earth Observatory - PHOTO: The Iliamna volcano is shown on Aug. 1, 2023, in Alaska.

On June 15, seismic activity ramped up at a "nearly continuous" rate for several hours, the observatory reported.

The Operational Land Imager, a sensor aboard the Landsat 8 satellite, acquired an image of the volcano on June 10, prior to when the rumblings began.

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The seismic activity was similar to those caused by the initial slipping between rock and ice that preceded large avalanches on the volcano in the past, according to the AVO.

Iliamna often experiences massive avalanches due to the combination of glacial ice weakened rock and volcanic heat, scientists say.

National Park Service - PHOTO: The Iliamna volcano is shown in Lake Clark National Park and Preserve in Alaska.

Its peak is covered in glaciers, snow and ice and it sits on a base of Jurassic-era granite, according to the NPS.

Since its last eruption, the volcano was recorded ejecting smoke and light ash in 1876, 1933, 1941 and 1947, according to the NPS.

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More reports of smoke and light ash were recorded for the late winter of 1956 or early spring of 1957, but those reports were not confirmed, the NPS said.

In 1958, four columns of vapor were shooting out of vents on the eastern side of the volcano, according to the NPS. But that was the last time smoke appeared to be ejected by the volcano.

NASA Earth Observatory - PHOTO: The Iliamna volcano in Alaska is shown in this NASA image on June 10, 2025.

Although Iliamna is remote -- located in the Chigmit Mountains within Lake Clark National Park and Preserve -- it is monitored closely be volcanologists due to its potential hazards. There are several communities within a 200-mile radius of the volcano that could be impacted in the event of an eruption, including Pedro Bay, Port Alsworth and Anchorage, according to the NPS.

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The AVO monitors 51 other active volcanos within the state, including the Redoubt Volcano, Iliamna's more eruptive neighbor, which is also located within the preserve.

The U.S. Geological Survey currently has Iliamna at a "normal" volcano alert level.