Massive Alaska landslide triggers raging tsunami with 10-15 foot crests
A massive landslide early Sunday morning near South Sawyer Glacier in Alaska’s Endicott Arm triggered a local tsunami, sending waves as high as 15 feet crashing through the remote fjord near Juneau.
Boaters in the area first reported the unusual wave activity near Harbor Island, according to the Alaska Earthquake Center. Three kayakers camping on the island lost most of their gear but safely returned to Juneau.
Initial wave estimates ranged from 10 to 15 feet near Harbor Island, but the National Park Service reported even more dramatic effects, with tsunami waves scraping trees from rocky slopes up to 100 feet high on nearby Sawyer Island.
Researchers initially found no evidence of an earthquake in the area, and the site fell outside the Earthquake Center’s standard landslide detection zones. However, Ezgi Karasözen, a research scientist at the center, applied a landslide analysis algorithm to seismic data and confirmed that a massive landslide—potentially involving over 100 million cubic meters of debris—had triggered the tsunami.
“This may be the largest landslide-triggered tsunami in Alaska since 2015,” Karasözen said.
Seismic activity related to the event was detected over 600 miles away. Small earthquakes had been occurring for over 18 hours leading up to the landslide.
Footage from a U.S. Coast Guard flyover showed a wide debris path down the mountainside near South Sawyer Glacier and along Tracy Arm Fjord.
Despite the size of the landslide and tsunami, no injuries or infrastructure damage were reported, according to the National Weather Service in Juneau.
Meanwhile, officials in Juneau are also monitoring a separate threat: the potential overflow of a glacial lake connected to the Mendenhall Glacier. Evacuation efforts are underway in low-lying areas due to the risk of major flooding.
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