(NewsNation) — A volcano in Alaska that last erupted in 1867 is displaying signs of rumbling. Located roughly 140 miles southwest of Anchorage, Iliamna has been dormant for over a century.

Caption Alaska’s Iliamna Lake harbor seals have been difficult to study because of their remoteness.

Alaska’s Iliamna Lake harbor seals commonly move more than 200 kilometers. Researchers hypothesized that they move regularly between freshwater and marine habitats.