Potential landslide-triggered tsunami threatens Prince William Sound

ANCHORAGE, Alaska (KTUU) - Geologists are warning that a large and dangerous tsunami could hit Prince William Sound if a landslide triggered a large enough wave.

The geologists, working at the Division of Geological and Geophysical Surveys, have noticed the rapid retreat of Barry Glacier in Barry Arm has the potential to release millions of tons of rock into Harriman Fjord. If this happens, geologists say a tsunami as large as state record-holding tsunamis could hit the area.

From: DGGS

Barry Arm is 28 miles northeast of Whittier and a potential landslide in this area could impact the city of 205 people. The unstable mountain slope above the glacier is 60 miles east of Anchorage and they believe a tsunami is likely to occur within the next 20 years. A letter signed by over a dozen researchers from multiple universities suggests that the tsunami-triggering landslide could occur within the next year.

Tsunami models by Patrick Lynett at the University of Southern California demonstrate a tsunami reaching hundreds of feet in elevation, with the ability to reach Whittier within 20 minutes. Other cities on the Prince William Sound, like Valdez and Cordova, could also see less destructive waves that may still be dangerous in harbors and docks.

For now, researchers are asking locals who have footage of Barry Arm, especially of rockfalls and rock slides, to share it with researchers as they work to understand how hazardous the change in slope is. The researchers with the Alaska Department of Natural Resources are requesting help from the U.S. Geological Survey to begin monitoring the area. The letter from researchers states their goal is to have the National Tsunami Warning Center monitor this landslide and provide warnings for landslide-generated tsunamis.

Alaska has experienced devastating tsunamis before, most notably in 1958 when a landslide in Lituya Bay Fjord in Glacier Bay hit the opposite side of the bay with a 1,700-foot wave.

“The most recent [tsunami] was at Southeast Alaska’s Taan Glacier in 2015, where a wave went 600 feet up the opposite wall of the glacial valley,” Director of the Division of Geological and Geophysical Surveys Steve Masterman said in a press release.

Geologists say its difficult to predict a landslide as variables such as rainfall, snowfall or seismic activity all impact a landslide. One thing that is certain is the continuing glacial retreat of Barry Glacier will increase the probability of a large landslide.

“As global warming continues to thaw glaciers and permafrost, landslide-created tsunamis are emerging as a greater threat – not just in Alaska, but in places like British Columbia and Norway,” Woods Hole Research Center in Massachusetts Scientist Anna Liljedahl said in a prepared statement.

Rick Green, a special assistant at Alaska Department of Fish and Game, said the region attracts a large number of boaters in the summer, with up to 500 people fishing, shrimping or camping at a time. For now officials at the Department of Natural Resources and Alaska Department of Fish and Game are urging people to stay away from danger zones in the region until scientists better understand the risk areas.

Landslides are a common source of giant waves for Alaska and Greenland. Back in June of 2017 a landslide at Karrat Fjord in Greenland generated a tsunami that destroyed a large portion of a town 20 miles away and killed four people. Survivors of the tsunami were unable to return to the town of Nuugaatsiaq because the area remains unstable. Geologists say the current unstable slope at Barry Arm is larger and has a greater potential to produce a significant tsunami than what was seen in Greenland.

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