The names may not be acquainted — Cowee Creek, Brabazon Vary, Higher Pederson Lagoon — however they mark the websites of latest lake tsunamis, a phenomenon that’s more and more widespread in Alaska, British Columbia and different areas with mountain glaciers.
Triggered by landslides into small our bodies of water, most of those tsunamis have occurred in distant places up to now, however geologist Bretwood Higman of Floor Reality Alaska mentioned it could simply be a matter of time earlier than a tsunami swamps a extra populated place like Portage Lake close to Whittier, Alaska.
When he estimates the place the chance of an Alaskan lake tsunami is highest, Portage Lake “is just about on the prime of my checklist,” Higman mentioned.
Different websites in Alaska the place the dangers of lake tsunamis coincide with human exercise and infrastructure embody Eklutna, Seward, Valdez, Juneau, Grewingk Lake in Kachemak Bay State Park and Index Lake close to Glacier View.
On the Seismological Society of America (SSA)’s 2024 Annual Assembly, Higman mentioned the significance of assessing websites like Portage Lake for the potential of lake tsunamis, partly by utilizing distinctive seismic indicators linked to landslides.
“There are some instances the place there are dramatic and really distinctive precursory seismic indicators that precede a catastrophic landslide, typically by as a lot as days,” Highman famous. “If we may get to the purpose the place we understood these and knew detect them, they could possibly be actually helpful.”
Higman calls lake tsunamis “an rising, climate-linked hazard.” The geological situations that underlie the occasions in locations like Alaska are normally comparable. Increased temperatures soften the glaciers that buttress the partitions of the valley that cradles the shrinking glacier. With out the glacier in place to carry them up, the valley partitions are extra vulnerable to landslide, both into an present physique of water or a brand new lake created by the glacier soften. In different areas, warming situations are weakening permafrost which may be vital to the soundness of slopes above lakes.
“That is one thing that traditionally has been a reasonably uncommon occasion, however in the previous couple of years there have been a extremely shocking variety of these,” mentioned Higman.
The 2020 Elliot Creek tsunami in a glacial valley in British Columbia, for example, featured a landslide measuring 18 cubic million meters in quantity and a tsunami runup of greater than 100 meters.
Forest and salmon habitat had been the primary casualties of that tsunami, however Higman and his colleagues are these distant however dramatic occasions to search out methods to arrange for tsunamis in locations with extra infrastructure. “There are locations the place we see the identical sorts of geologic instability that preceded these different occasions, however there are lots of people uncovered,” mentioned Higman.
Higman mentioned there are some parallels between the tectonic faults that seismologists normally examine and “the behaviors that we’re seeing within the failure floor of those very giant landslides,” suggesting that in addition they provide one solution to examine fault dynamics in miniature.