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Newly-discovered landslide in Barry Arm also has potential to create destructive tsunami

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barry arm(DGGS)
Published: Dec. 30, 2020 at 9:41 PM AKST
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ANCHORAGE, Alaska (KTUU) - Scientists say there is a second, newly-discovered landslide in Barry Arm that has the potential to create a destructive tsunami to areas around Prince William Sound, including Whittier, about 30 miles away.

Scientists previously discovered a larger landslide right next to the new one.

The fjord wall was once supported by Barry Glacier before it rapidly retreated leaving the masses sitting high above sea level.

Alaska Department of Natural Resources Division of Geological and Geophysical Surveys Geohydrologist Ronald Daanen said this landslide is much smaller, but the tsunami it has the potential to create could be just as big.

Daanen said the smaller landslide may not be as big, “but it is moving faster. And it is at a little bit higher elevation. And it is right above a section of Barry Arm that is deeper.”

He said the newly discovered slide is on average about 750 meters above sea level.

“There is a lot of speed that can be gained from all that rock,” he said.

The slide is thought to be about 16 million cubic meters.

“It is definitely not a small amount,” Daanen said. “It is for sure going to generate a tsunami if it goes similar to the large landslide.

“And I think that this smaller mass is a little bit more imminent because it is actually moving at a rate that is not sustainable for that rock landslide because rock is very unstable. And if you move it a little bit, then you could lose that hold on the mass,” Daanen said.

While data shows the original, bigger landslide is slowly moving on again off again, the newly-discovered landslide looks to be moving at a concerning rate.

Norwegian scientists have more experience with this type of landslide. They have settled on a specific rate of movement that prompts evacuations.

“If this would be a Norwegian fjord, and this particular mass would show this kind of movement, people would be alarmed, and they would probably evacuate,” Daanen said.

But, he said Barry Arm is not a Norwegian fjord and the rocks are likely not the same.

“We don’t think that everybody should be evacuating, especially not if you have potentially 20 minutes of time before tsunami hits [Whittier].

“Basically, what we are saying is that the threat is still there. A landslide could happen at any time in Barry Arm.”

Daanen said even though the bigger, previously known landslide isn’t moving as much right now, his team does think that it still has the potential to start moving again and become a bigger threat.

“But now that we have detect a smaller one, it basically is the same problem. There is a landslide and it is moving. And it could cause a tsunami,” he said.

Seismic stations were placed in September to monitor the original slide allowing data to be collected more often.

Dave Snider with the tsunami warning center says they are working on incorporating tsunamis triggered by landslides into the local warning system, however, he said the water level sensors won’t be deployed until spring.

“We definitely do not have a proper warning system,” Daanen said. “We do our best, and we can do more.”

He said winter makes it more difficult to collect data.

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