Landslide in Alaska threatens to trigger historic mega-tsunami

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An ongoing landslide between two glaciers in south-central Alaska could cause a tsunami in the region to rival anything seen in modern times, leading state authorities to ask boaters and others to avoid the area if possible.

The unstable piece of slope is estimated at around 500 million cubic meters and sits on a long, steep drop above Prince William Sound’s Barry Arm, about 30 miles from the small town of Whittier.

While the slope has been unstable for decades, new initiatives in the past decade have provided new data on its movement. After the movement appeared to slow, movement was detected again on August 23, 2022, and the magnitude of the movement increased over the next two months, prompting the Geological and Geophysical Surveys Division of the Alaska (ADGGS) to begin issuing regular warnings.

“Due to the current danger, we ask people to use their best judgment and, where possible, limit travel in the Barry Arm area, including Harriman Fjord, Barry Arm, College Fjord and Upper Port Wells” , reads the latest status update from October 21.

Previous research with support from NASA has suggested that if the entire unstable mass were to slide into the water below, it could trigger a historic mega-tsunami an order of magnitude larger than the 1958 landslide and tsunami. in Lituya Bay (southeast Alaska), the largest of its kind. modern day event.

In this case, an earthquake triggered a massive landslide that generated a mega-tsunami with a wave that reached a dizzying height of over 1,700 feet.

In the case of the Barry Arm landslide, it has already been seen to move up to several centimeters per day in recent weeks. A breakdown can occur at any time, although it’s unclear exactly how big such a slide might be or how much material might fall into the water.

“There are a lot of unknowns, including the thickness of the moving mass,” writes landslide expert Dave Petley for AGU. “Unfortunately, access is currently restricted due to the risk associated with being on water near the landslide.”

There are few major population centers nearby, but ADGGS notes that a tsunami “could have devastating local effects on those who live, work and play in and around Whittier and northern Prince William Sound”.

“Early research indicates that other communities and infrastructure in Prince William Sound could also be exposed to measurable tsunami and dangerous currents, including Valdez, Cordova, Tatitlek and Chenega.”

The worst case scenario would of course be for a major earthquake to hit the area and cause the entire slope to collapse. Such tremors are not unheard of in this part of the world, leaving the waters around Barry Arm marked as a danger zone for the foreseeable future.

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