Upper Pedersen Lagoon began appearing in the 1960's as Pedersen Glacier receded.
A landslide occurred in the early morning on Wednesday, August 7th, 2024, approximately 04:55 AKDT / 12:55 UTC, at a latitude/longitude of approximately 59.9038N, 149.8246W, on a southwest-facing slope to the north of Pedersen Glacier. Preliminary surveying indicated that a 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. 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.
Upper Pedersen Lagoon has experienced at least one other landslide-generated tsunami in April 2022.
