August 10, 2025 Tsunami: Tracy Arm, AK, United States

Ref #14369:

Early in the morning of 10 August 2025, a >64 × 106 m3 landslide struck Tracy Arm fjord in Alaska. The landslide was preconditioned by glacial retreat caused by climate change. The resulting 481 m runup megatsunami followed an initial 100-m high breaking wave traveling >70 m s−1 […] The most distal traces of tsunami runup and erosion are ~50–55 km from the landslide, in Holkham Bay (16 m elevation), a few km east of the kayaker camp, and at Williams Cove (35 m elevation from field survey)

Ref #14163:

Using GPS and altimeter readings from the helicopter, they estimated tsunami run-up on the hillslope opposite the landslide to be between 470 to 500 meters (1,500-1,600 feet) high

Reference #14135:

A landslide at Endicott Arm south of Juneau early Sunday morning caused a tsunami across much of Southeast Alaska with waves up to 15 feet high, according to the Alaska Earthquake Center. "We are working with other agencies and colleagues to understand the full sequence of events, but at this point, all evidence suggests that this set of reported 10-15-foot high waves was set in motion by a landslide of several tens of millions of cubic meters of rock striking the water,"

No deaths or major damage were reported from the tsunami that appeared to originate from Endicott Arm shortly after 5:30 a.m., according to the center

"We had an unfortunate incident on Harbour Island, where a landslide /iceberg caused a tidal surge and swept half of our gear away at Tracy Arm inlet," the message posted by Sasha Calvey of Inside Passage Sea Kayakers states. “We lost one boat, much of our personal gear, and a good chunk of our cooking equipment and group gear. All is good we headed to Juneau. We looking for a place to set up our tent or have a place to stay as we figure out the remaining of our logistics.”

Ref #14138:

A landslide above the terminus of Sawyer Glacier occurred at 13:26 UTC / 05:26 AKDT on Sunday, 10 August 2025. A tsunami was generated when this landslide entered the waters of Tracy Arm. Wave of 3-4.5 m (10-15’) in height were reported nearby, and photographs from the Arm show vegetation damage extending 20 m (~70’) above the water level. Higher wave heights are likely closer to the source.

The landslide generated seismic waves that allow for locating and estimating the volume of the landslide and defining the duration of the landslide event.

Preliminary estimates indicate that the landslide was ~100 M m3. The duration of the landslide was approximately 2 minutes.

This landslide entered the waters of Tracy Fiord and generated a tsunami that was observed by a group of sea kayakers who were camping near the mouth of Endicott Arm.

Photos from Tracy Arm (exact location not yet know) show that the tsunami damaged shoreline vegetation to a height of ~20m above the water level. The tsunami occurred near low tide, thereby reducing the scale of impact on the shoreline. A small tsunami with a maximum wave height of approximately 36 cm (1.2’) was recorded in Juneau at tide gauges operated by the National Tsunami Warning Center 60 minutes after the failure of the landslide.

Ref #14139:

The National Park Service reported a run-up of at least 100 ft [~30 m] at Sawyer Island, with vegetation stripped from the slopes.

The National Weather Service office in Juneau reported no known injuries or infrastructure impacts.

This event is extremely interesting scientifically. The landslide was preceded by hours of small magnitude 1-2 earthquakes leading up to the slide.

The precursors are very clear in the ~18 hrs prior to the slide and likely well before that. Our seismic data analysts have analyzed about a hundred of these precursors and they emanate from the same area as the landslide