The Alaska Volcano Observatory said signs indicated a Mount Spurr eruption was likely, though not certain, in the weeks or months ahead.

Researchers predict the most likely outcome of the unrest at Mt. Spurr is “one or more explosive events” that could last as long as a few hours and produce ash clouds carried for hundreds of miles.

Alaska’s Mount Spurr, a volcano about 80 miles away from the state’s largest city, will “likely” erupt in the coming weeks or months for the first time in over 30 years,