2024 Pedersen Lagoon Landslide-Generated Tsunami
A landslide produced a tsunami in Pedersen Lagoon, southwest of Seward, Alaska on Wednesday, August 7th, 2024, at approximately 04:55 AKDT / 12:55 UTC. Preliminary surveying indicates that the landslide generated a tsunami of 17 meters high (approx. 56 ft) or more in Upper Pedersen Lagoon, reducing to about one meter high (approx. 3 feet) in Lower Pedersen Lagoon. Runup heights reported here are preliminary and are subject to change with additional field validation. No injuries or fatalities have been reported. This page may be updated as more information about the event is obtained.
This landslide event page serves as an event summary to communicate timely science information to multiple audiences. This information includes what is currently understood about the event and ongoing activities of the USGS and partner agencies.
| Disclaimer: This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely science to assess ongoing hazards. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information. |
Satellite imagery, an overflight, geophysical data, and field reconnaissance provided the observations for the following summary.
Field Photos | Updates | More Information | Publications
Update - 2024-08-21
A landslide occurred in the early morning on Wednesday, August 7th, 2024, at a latitude/longitude of approximately 59.9038N, 149.8246W, on a southwest-facing slope to the north of Pedersen Glacier. The landslide traveled along the glacier and entered Upper Pedersen Lagoon, producing a local tsunami that traveled across the upper lagoon to Lower Pedersen Lagoon, where it damaged wooden boardwalks in the tidal zone at a lodge and impacted a National Park Service campsite easement. No known injuries or fatalities were reported. Witnesses at the lodge reported a loud "thunderous sound" and witnessed "a two-to-three-foot wave or set of waves that flowed up to the cabins." The tide was ebbing and reportedly 3 meters (approx. 10 feet) at the time of the event. Photos from an overflight on August 9th, 2024 confirmed the landslide occurrence and location.
Preliminary ground-based surveying by the National Park Service indicates that the tsunami was on the order of 17 meters high (approx. 56 ft) on the east side of the upper lagoon, traveled across a portion of the landform between the two lagoons, and reduced to about one meter high (approx. 2-3 feet) in eastern portions of the lower lagoon. The earliest geophysical detections were done by the USGS National Earthquake Information Center and the Alaska Earthquake Center using seismic data, which indicates that the landslide occurred at 04:54:49 AKDT / 12:54:49 UTC. During the tsunami event, seismic signals suggest that a seiche, or an oscillating wave, likely formed.
Preliminary volume estimates based on seismic data1 indicate that the landslide was on the order of 2 million cubic meters (2.6 million cubic yards). This volume estimate is preliminary and subject to change with additional data. The landslide occurred in a rock unit called the Chugach flysch, which is composed of tectonically deformed and metamorphosed sandstone and siltstone that formed 145 to 66 million years ago2.
Background
Landslides that form above, and which could fail into waterbodies including lakes, fiords, and bays, are relatively common in the steep and glaciated mountains of Alaska3,4,5. Upper Pedersen Lagoon has experienced at least one other landslide-generated tsunami in April 2022, which is not known to have reached the lodge on the eastern shore of the Lower Pedersen Lagoon. As populations, infrastructure, recreation, and commercial activities expand into lakes and coastal waterways where landslides are common, risks increase. The U.S. Geological Survey (USGS) and our partners at the Alaska Division of Geological & Geophysical Surveys (DGGS), National Oceanic and Atmospheric Administration (NOAA), Alaska Earthquake Center (AEC), and National Park Service (NPS) are engaged in scientific studies to better understand the extent and magnitude of the hazard presented by landslides and landslide-generated tsunami in Alaska’s coastal waterways and large lakes.
Contributors to this page include Lauren Schaefer (USGS), Marísa Macías (USGS), Liam Toney (USGS), Stephen Slaughter (USGS), Dennis Staley (USGS), Matt Haney (USGS), Nicole Abib (NPS), Sarah Venator (NPS), Ezgi Karasözen (AEC), and Kirk Hoessle and Jeff Pedersen (Alaska Wildland Adventures).
More Information
Read the Kenai Fjords National Park press release.
Learn more about the Kenai Fjords National Park.
Learn more about the Landslide Hazards Program.
Learn more about USGS Landslide Response.
References
1Karasözen, E. and West, M.E., 2024, Toward the Rapid Seismic Assessment of Landslides in Coastal Alaska: The Seismic Record 4(3), 43–51. https://doi.org/10.1785/0320230044
2Wilson, F.H., Hults, C.P., Mull, C.G, Karl, S.M, 2015, Geologic map of Alaska: U.S. Geological Survey Scientific Investigations Map 3340, pamphlet 196 p., 2 sheets, scale 1:1,584,000. https://doi.org/10.3133/sim3340
3Miller, D.J, 1960, The Alaska earthquake of July 10, 1958: Giant wave in Lituya Bay: Bulletin of the Seismological Society of America 50(2): 253-266. https://doi.org/10.1785/BSSA0500020253
4Coe, J.A., Bessette-Kirton, E.K., and Geertsema, M., 2018, Increasing rock-avalanche size and mobility in Glacier Bay National Park and Preserve, Alaska detected from 1984 to 2016 Landsat imagery: Landslides 15, 393–407. https://doi.org/10.1007/s10346-017-0879-7
5Schaefer, L.N., Kim, J., Staley, D.M., Lu, Z., and Barnhart, K.R., 2024, Satellite interferometry landslide detection and preliminary tsunamigenic plausibility assessment in Prince William Sound, southcentral Alaska: U.S. Geological Survey Open-File Report 2023–1099, 22 p., https://doi.org/10.3133/ofr20231099
A landslide produced a tsunami in Pedersen Lagoon, southwest of Seward, Alaska on Wednesday, August 7th, 2024, at approximately 04:55 AKDT / 12:55 UTC. Preliminary surveying indicates that the landslide generated a tsunami of 17 meters high (approx. 56 ft) or more in Upper Pedersen Lagoon, reducing to about one meter high (approx. 3 feet) in Lower Pedersen Lagoon. Runup heights reported here are preliminary and are subject to change with additional field validation. No injuries or fatalities have been reported. This page may be updated as more information about the event is obtained.
This landslide event page serves as an event summary to communicate timely science information to multiple audiences. This information includes what is currently understood about the event and ongoing activities of the USGS and partner agencies.
| Disclaimer: This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely science to assess ongoing hazards. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information. |
Satellite imagery, an overflight, geophysical data, and field reconnaissance provided the observations for the following summary.
Field Photos | Updates | More Information | Publications
Update - 2024-08-21
A landslide occurred in the early morning on Wednesday, August 7th, 2024, at a latitude/longitude of approximately 59.9038N, 149.8246W, on a southwest-facing slope to the north of Pedersen Glacier. The landslide traveled along the glacier and entered Upper Pedersen Lagoon, producing a local tsunami that traveled across the upper lagoon to Lower Pedersen Lagoon, where it damaged wooden boardwalks in the tidal zone at a lodge and impacted a National Park Service campsite easement. No known injuries or fatalities were reported. Witnesses at the lodge reported a loud "thunderous sound" and witnessed "a two-to-three-foot wave or set of waves that flowed up to the cabins." The tide was ebbing and reportedly 3 meters (approx. 10 feet) at the time of the event. Photos from an overflight on August 9th, 2024 confirmed the landslide occurrence and location.
Preliminary ground-based surveying by the National Park Service indicates that the tsunami was on the order of 17 meters high (approx. 56 ft) on the east side of the upper lagoon, traveled across a portion of the landform between the two lagoons, and reduced to about one meter high (approx. 2-3 feet) in eastern portions of the lower lagoon. The earliest geophysical detections were done by the USGS National Earthquake Information Center and the Alaska Earthquake Center using seismic data, which indicates that the landslide occurred at 04:54:49 AKDT / 12:54:49 UTC. During the tsunami event, seismic signals suggest that a seiche, or an oscillating wave, likely formed.
Preliminary volume estimates based on seismic data1 indicate that the landslide was on the order of 2 million cubic meters (2.6 million cubic yards). This volume estimate is preliminary and subject to change with additional data. The landslide occurred in a rock unit called the Chugach flysch, which is composed of tectonically deformed and metamorphosed sandstone and siltstone that formed 145 to 66 million years ago2.
Background
Landslides that form above, and which could fail into waterbodies including lakes, fiords, and bays, are relatively common in the steep and glaciated mountains of Alaska3,4,5. Upper Pedersen Lagoon has experienced at least one other landslide-generated tsunami in April 2022, which is not known to have reached the lodge on the eastern shore of the Lower Pedersen Lagoon. As populations, infrastructure, recreation, and commercial activities expand into lakes and coastal waterways where landslides are common, risks increase. The U.S. Geological Survey (USGS) and our partners at the Alaska Division of Geological & Geophysical Surveys (DGGS), National Oceanic and Atmospheric Administration (NOAA), Alaska Earthquake Center (AEC), and National Park Service (NPS) are engaged in scientific studies to better understand the extent and magnitude of the hazard presented by landslides and landslide-generated tsunami in Alaska’s coastal waterways and large lakes.
Contributors to this page include Lauren Schaefer (USGS), Marísa Macías (USGS), Liam Toney (USGS), Stephen Slaughter (USGS), Dennis Staley (USGS), Matt Haney (USGS), Nicole Abib (NPS), Sarah Venator (NPS), Ezgi Karasözen (AEC), and Kirk Hoessle and Jeff Pedersen (Alaska Wildland Adventures).
More Information
Read the Kenai Fjords National Park press release.
Learn more about the Kenai Fjords National Park.
Learn more about the Landslide Hazards Program.
Learn more about USGS Landslide Response.
References
1Karasözen, E. and West, M.E., 2024, Toward the Rapid Seismic Assessment of Landslides in Coastal Alaska: The Seismic Record 4(3), 43–51. https://doi.org/10.1785/0320230044
2Wilson, F.H., Hults, C.P., Mull, C.G, Karl, S.M, 2015, Geologic map of Alaska: U.S. Geological Survey Scientific Investigations Map 3340, pamphlet 196 p., 2 sheets, scale 1:1,584,000. https://doi.org/10.3133/sim3340
3Miller, D.J, 1960, The Alaska earthquake of July 10, 1958: Giant wave in Lituya Bay: Bulletin of the Seismological Society of America 50(2): 253-266. https://doi.org/10.1785/BSSA0500020253
4Coe, J.A., Bessette-Kirton, E.K., and Geertsema, M., 2018, Increasing rock-avalanche size and mobility in Glacier Bay National Park and Preserve, Alaska detected from 1984 to 2016 Landsat imagery: Landslides 15, 393–407. https://doi.org/10.1007/s10346-017-0879-7
5Schaefer, L.N., Kim, J., Staley, D.M., Lu, Z., and Barnhart, K.R., 2024, Satellite interferometry landslide detection and preliminary tsunamigenic plausibility assessment in Prince William Sound, southcentral Alaska: U.S. Geological Survey Open-File Report 2023–1099, 22 p., https://doi.org/10.3133/ofr20231099