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Rock and glacial ice slide in the Endicott Arm area of Alaska generates 15 feet tsunami waves in fjord.
A US Coast Guard helicopter video showing a landslide scar that struck an Alaska fjord near Juneau. The massive slide, containing rock and glacial ice, barreled into the Ocean, generating up to 20-foot tsunami waves. It was sparsely populated, and only kayakers who were able to return to Juneau were involved. The tsunami removed the treeline 20 feet high.
It has been a busy couple of days! There was a large landslide and tsunami in SE Alaska, in Tracy Arm, Sunday morning. Luckily, no injuries or casualties were reported. This region is outside of our current landslide coverage, but we were able to get a quick location after hearing about the event. 🧵
— Dr. Ezgi Karasozen (@ezgikarasozen.bsky.social) 2025-08-13T02:29:53.444Z
The landslide occurred on the same day as the Glacial Outburst Flood in Junea. No information is available on whether the two events are related.
From the Earthquake Center, University of Alaska:
Early on August 10, the Earthquake Center received reports from people out boating of a mysterious local tsunami in the Endicott Arm area of Southeast Alaska, with waves of 10–15 ft near Harbor Island (Figure 1). The National Park Service reported a run-up of at least 100 ft at Sawyer Island, with vegetation stripped from the slopes. (Figure 2)
Three kayakers camping at Harbor Island lost most of their gear, but made it safely back to Juneau. Nick Heilgeist, one of the kayakers, said “We were woken up somewhere 5:45-6 by the water rushing by 1 ft from our tent back in the woods.” Heilgeist said it was nearly low tide. They were camped well above the expected 17-foot high tide, so he estimated the wave probably came about 20 vertical feet.
The National Weather Service office in Juneau reported no known injuries or infrastructure impacts. The National Tsunami Warning Center reported the highest wave as 14 inches (35 cm) on the Juneau tide gauge, about 60 miles away.
That same morning, Ezgi Karasözen, one of the Earthquake Center’s research scientists involved in developing tools to detect landslides, jumped on the mystery. There was no earthquake detected in the area. The region is outside of the Earthquake Center’s recently expanded landslide detection coverage, so there was no automatic detection. Karasözen applied our landslide characterization algorithm on the data from Southeast Alaska seismic stations (Figures 3-5).
What she found in the seismic record was a massive landslide in the same area as the tsunami. “Our initial estimate placed the source near South Sawyer Glacier, with a very large volume, possibly larger than 100 million cubic meters,” said Karasözen. There is some uncertainty of the actual volume, but it will take several days at least to ground-truth the event, and these are the first, rapid estimates of its size.“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,”said Karasözen.
Three kayakers camping at Harbor Island lost most of their gear, but made it safely back to Juneau. Nick Heilgeist, one of the kayakers, said “We were woken up somewhere 5:45-6 by the water rushing by 1 ft from our tent back in the woods.” Heilgeist said it was nearly low tide. They were camped well above the expected 17-foot high tide, so he estimated the wave probably came about 20 vertical feet.
The National Weather Service office in Juneau reported no known injuries or infrastructure impacts. The National Tsunami Warning Center reported the highest wave as 14 inches (35 cm) on the Juneau tide gauge, about 60 miles away.
That same morning, Ezgi Karasözen, one of the Earthquake Center’s research scientists involved in developing tools to detect landslides, jumped on the mystery. There was no earthquake detected in the area. The region is outside of the Earthquake Center’s recently expanded landslide detection coverage, so there was no automatic detection. Karasözen applied our landslide characterization algorithm on the data from Southeast Alaska seismic stations (Figures 3-5).
What she found in the seismic record was a massive landslide in the same area as the tsunami. “Our initial estimate placed the source near South Sawyer Glacier, with a very large volume, possibly larger than 100 million cubic meters,” said Karasözen. There is some uncertainty of the actual volume, but it will take several days at least to ground-truth the event, and these are the first, rapid estimates of its size.“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,”said Karasözen.