() 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. But on June 15, the Alaska Volcano Observatory detected seismic activity.

Scientists believe the shaking was likely caused by a large avalanche. Iliamna is known for frequent ice and rock slides that cause the mountain to rumble every couple of years.

While not a clear sign of imminent eruption, the event highlights the dynamic nature of this glacier-covered peak, which stands 10,000 feet tall.

As of July 4, Iliamna Volcano’s threat level is categorized as “Green/Normal,” according to the United States Geological Survey.