Lake tsunamis are an emerging climate-linked hazard

The relatively obscure locations of Cowee Creek, Brabazon Range, and Upper Pederson Lagoon have recently become significant for their experience with lake tsunamis – a growing phenomenon primarily noted in Alaska and British Columbia, driven by the effects of climate change on mountain glaciers.

Lake tsunamis are typically triggered by landslides that plunge into small, often remote bodies of water. 

Potential for lake tsunamis 

While most lake tsunamis have occurred away from populous areas, geologist Bretwood Higman from Ground Truth Alaska warns of the potential for such events to impact more inhabited locations, particularly Portage Lake near Whittier.

According to Higman, places like Eklutna, Seward, Valdez, Juneau, Grewingk Lake in Kachemak Bay State Park, and Index Lake near Glacier View also carry significant tsunami risk with human activity and infrastructure.

During the Seismological Society of America (SSA)’s 2024 Annual Meeting, Higman highlighted the necessity of monitoring such locations for potential lake tsunamis, particularly through the lens of unique seismic signals that landslides often produce.

“There are some cases where there are dramatic and very distinctive precursory seismic signals that precede a catastrophic landslide, sometimes by as much as days,” Higman explained. “If we could get to the point where we understood these and knew how to detect them, they could be really useful.”

Warming conditions enhance risks

Labeling lake tsunamis as an “emerging, climate-linked hazard,” Higman detailed how geological conditions that foster such events are generally consistent across different locales. 

The melting of glaciers, exacerbated by rising temperatures, weakens the support they provide to adjacent valley walls, increasing their susceptibility to landslides into either existing water bodies or new lakes formed from the glacial melt. 

Additionally, warming conditions contribute to the degradation of permafrost that stabilizes mountain slopes, further enhancing risks.

More frequent lake tsunamis 

The phenomenon has been observed more frequently in recent years, with the 2020 Elliot Creek tsunami in a British Columbian glacial valley serving as a stark example. 

This event involved a landslide that displaced 18 million cubic meters of earth and caused tsunami waves that ran up more than 100 meters, devastating local forest and salmon habitats.

Preparing for future lake tsunamis 

Although lake tsunamis currently affect less populated areas, Higman and his colleagues are using the data gathered from such incidents to develop preparedness strategies for potentially affected communities with significant infrastructure. 

The researchers are studying geological instabilities similar to those that have led to past tsunamis, hoping to mitigate risks for densely populated regions.

Finally, Higman suggests that examining these massive landslide events could offer insights into tectonic fault behaviors, providing a smaller-scale model for understanding seismic activities more broadly. 

More about lake tsunamis 

Lake tsunamis, also known as seiches, are large waves or series of waves generated in enclosed or semi-enclosed bodies of water like lakes, bays, or reservoirs. 

Causes

Unlike oceanic tsunamis that are commonly caused by seismic activity (earthquakes, volcanic eruptions, or landslides), lake tsunamis often result from sudden changes in atmospheric pressure, strong winds, or rapid displacement of water caused by landslides or large objects falling into the lake.

The phenomenon occurs when the water in a lake is pushed from one end to the other, piling up and then oscillating back and forth until it loses energy and stabilizes.

These oscillations can be amplified by the shape of the lake, especially if it is long and narrow, which can cause the wave heights to increase significantly as they travel back and forth.

Lake Michigan 

One famous historical example of a seiche occurred in 1954 at Lake Michigan, where strong winds and rapid changes in atmospheric pressure resulted in waves that reached up to 10 feet high, causing substantial damage along the Chicago waterfront.

Another notable instance happened in Switzerland’s Lake Geneva in the 6th century, triggered by a massive rockfall.

Significant risks

Although lake tsunamis are less common and generally less destructive than their oceanic counterparts, they can still pose significant risks to those living near or on bodies of water, especially in regions prone to sudden meteorological changes or seismic activity.

Precautions and early warning systems can help mitigate the impact of such events, enhancing safety for communities in vulnerable areas.

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