On August 10th, 2025, the Alaska Earthquake Center received reports of a mysterious localized tsunami that produced waves of 10-15 feet. The tsunami occurred in the Endicott Arm area of Southeast Alaska, with waves reaching the 10-15 foot height near Harbor Island. No earthquakes had occurred in the area to cause the tsunami. Officials later determined that a major landslide collapsed onto the South Sawyer Glacier and Tracy Arm Fjord, about 60 miles southeast of Juneau, leading to the tsunami.
Local Tsunami in Southeast Alaksa
According to the National Park Service, the localized tsunami caused run-up of at least 100 feet at Sawyer Island, stripping vegetation from the slopes. At Harbor Island, three kayak campers lost a most of their gear in the wave. Nick Heilgeist, on of the kayakers, said it was nearly low tide when the wave occurred. They had set up camp far above the expected 17-foot high tide, so he believed the wave came up about 20 vertical feet. Fortunately all three made it safely back to Juneau.
“We were woken up somewhere 5:45-6 by the water rushing by 1 ft from our tent back in the woods.” – Nick Heilgeist.
The Juneau National Weather Service office reported no known injures or infrastructure impacts. The National Tsunami Warning Center put the highest wave at 14 inches on the Juneau tide gauge about 60 miles away.
Landslide at the South Sawyer Glacier
Ezgi Karasözen, one of the Alaska Earthquake Center’s research scientists involved in developing tools to identify landslides, applied a landslide characterization algorithm on the data from Southeast Alaska seismic stations. She was able to to locate a massive landslide in the area of the tsunami.
“Our initial estimate placed the source near South Sawyer Glacier, with a very large volume, possibly larger than 100 million cubic meters. Our goal with these initial estimates is to get a quick ballpark estimate of what’s going on. I’m sure there will be lots of detailed volume estimates coming from various studies, but it will take time.” – Ezgi Karasözen
The recent incident could mark the largest landslide and tsunami in Alaska since Taan Fjord in 2015. Seismic stations further than 600 miles away picked up on the landslide signal.
