Landslide triggers 55-foot tsunami wave at Kenai Fjords National Park

A remote landslide produced a tsunami last month at Kenai Fjords National Park near Seward.

No injuries or fatalities were reported, but the wave caused minor damage to a privately-owned boardwalk. It also moved a Park Service campground food storage box about 20 feet.

According to the National Park Service, the Aug. 7 landslide splashed down into the upper part of Pedersen Lagoon about 20 miles southwest of Seward, producing a wave about 55 feet high. Then it crossed over a ridge and flowed into the lower part of the lagoon, hitting the shore at a height of about 3 feet.

Chad Hults, the Park Service’s regional geologist for Alaska, said the slope above the water is unstable. As a result, the landslide and tsunami didn’t come as a surprise.

“The landslide gave way during a very significant rain event that happened that week, I believe it was around 15 inches of rain that fell that week,” Hults said.

Hults said the region has seen several landslides within the last few years, and that heavy rains and thinning glaciers are making them more common.

“People should be careful about travel and understand when there’s heavy rain events, those are times when landslides can be triggered, and they can hit the water and generate tsunamis,” he said.

The Park Service recommends visitors to Pedersen Lagoon take precautions for the possibility of other landslides or tsunamis.