Giant waves in calm waters: Find out why lake tsunamis are so dangerous

During the Seismological Society of America (SSA) meeting held in Anchorage, Alaska, A threatening statement on a little-known topic: lake tsunamis. Citing the locations of Cowee Creek, the Brabazon Range and the Upper Pederson Lagoon, Bretwood Higman from the NGO Ground Truth Alaska said that these are examples of lake tsunamis that occur in Alaska.

Most of these giant waves, created by landslides in small streams, have so far occurred in remote locations, but according to Higman, it’s only a matter of time before a tsunami hits communities like Portage Lake near the city of Whittier. warns Higman in Alaska.

Looking at the list of places at risk, Higman said Portage Lake was “pretty much at the top of my list.” Since it is a retreating tidal glacier, it flows into the lake and eventually into the sea. In addition to Whittier, the list also includes more populous cities such as Eklutna, Seward, Valdez and Alaska’s capital Juneau.

How do tsunamis occur in lakes?

In the same way as ocean tsunamis resulting from underwater events (earthquakes, volcanic eruptions or landslides), Lake tsunamis are also caused by seismic activities. Such events can disrupt the lake bed and displace large amounts of water.

In his presentation, Higman explained that lake tsunamis, in the case of Alaska and British Columbia (in Canada), represent an “emerging climate-related hazard.”

With global warming, the glaciers that support the valley walls around them are melting. This can increase the risk of landslides that can cause tsunamis in existing bodies of water or even in lakes formed by melting glaciers.

Are lake tsunamis dangerous?

Lake tsunamis are always catastrophic, regardless of the region in which they occur. The highest of these occurred in Alaska in July 1958. It caused waves up to 524 meters high and occurred in a fjorda type of glacial valley flooded by the sea. This was due to a 7.9 magnitude earthquake that triggered a massive landslide on the mountainside.

Another massive landslide (18 million cubic meters of rock) occurred in British Columbia in November 2020. causing a tsunami in the lake with waves up to 100 meters high. This event devastated the entire land, including an old stream called Elliot Creek.

Geomorphologist Marten Geertsema described the scene in an interview with CBC: “Imagine a landslide with a mass equal to all the cars in Canada, moving at about 140 kilometers per hour and crashing into a large lake.”

Is there anything you want to ask? Tell us about our social networks and seize the opportunity to understand why ocean waves pose a complex challenge in nonlinear science.