An unstable slope over Prince William Sound is descending faster. A complete failure could cause a tsunami.

Last month, scientists noticed new movement in an unstable slope in Prince William Sound, but they aren’t sure where that new movement may lead.

It’s possible the increased speed means rapid slope failure, which could cause the landmass to crash into the water below. That could, in turn, create a tsunami in nearby fjords and bays, as well as dangerous flooding, waves and currents in the community of Whittier, a risk that scientists first warned about in 2020.

But it is also possible that the movement stops and nothing dramatic or devastating happens.

The steep slope is located in Barry Arm Fjord, on a narrow stretch of water in Prince William Sound. It is located 30 miles northeast of Whittier.

Dennis Staley, a research physical scientist with the US Geological Survey who leads the Prince William Sound Landslide Hazards Project, said in late August that scientists noticed a portion of the unstable area began to move.

The movement caused concern because of how quickly the slope went from not moving to sliding about 50 millimeters a day for a few days, Staley said.

“We don’t like the speeding up of landslides; that makes us a little nervous,” Staley said. “And then we also don’t like to see the area that is expanding.”

It’s challenging, if not impossible, to say how likely it is that the slope will fail on any given day or during a specific period, Staley said. They can’t tell if the slope will keep moving and stop at some point, or if a rapid landslide is possible, known as catastrophic failure.

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“We don’t want to be too alarmist and say this is something that will inevitably end in catastrophic failure because there’s a very good chance it won’t, but we want to watch out for the avalanche,” he said. she said.

Staley said that scientists have suspended non-essential boat activities at Barry Arm as a precaution.

“We don’t want to put our crews in harm’s way if some kind of failure occurs,” Staley said.

There are a few potential scenarios for what could happen if the slope fails, said Seldovia-based geologist Bretwood Higman, who investigated Barry Arm. Higman’s sister, an artist and naturalist, was the person who initially flagged the slope as potentially unstable while she was in the area.

The impacts of possible slope failure depend on the size of the area hitting the water and the amount of water it would displace, Higman said. He noted that the level of uncertainty is high: They don’t know how damaging the impacts would be to the city of Whittier. However, he said they would likely be at least problematic in terms of strong currents that could damage the port. Different models have shown waves of different sizes reaching the community, Higman said.

Higman said there’s no right answer for people trying to decide whether or not they should spend time around the Barry Arm.

“We don’t know enough about it to pretend we can tell someone what to do,” Higman said.

For his part, Higman said he would not camp on the beach in the Barry and Harriman Fjord areas, given the dangers even a small tsunami would pose to the site. He would also be careful to grab a container just below the area of ​​instability.

“Those aren’t craps that I’m comfortable rolling, but that’s who I am,” Higman said. “Really, I absolutely wouldn’t judge another person who makes a different decision.”

[Correction: An earlier version of this story included an incorrect spelling of Harriman.]