![]() ![]() Most of the research on tsunami impacts has focused on longer-period regional tsunamis-especially subduction zone earthquake tsunamis that produce some of the longest period waves. Tsunamis generated by subaerial landslides are often confined to a few tens of kilometers around the landslide, both because shorter-period waves disperse energy more quickly and because they commonly are triggered in relatively confined bays and lakes. These tsunamis may reach several hundred meters above the water, but affect a much smaller area than their long-period cousins. They crash ashore more like a wind wave, rising to their peak elevations within a few minutes at most. In contrast, tsunamis generated by subaerial landslides (as well as ice-calving and meteor impacts) are often much shorter-period, flooding the land more rapidly, and affect a smaller area. These long-period tsunamis usually take up to a half-hour to inundate elevations less than twenty meters above the water. They can impact areas as large as entire ocean basins, but with shorter runups (they run up from the coast to lower elevations), as happened with the Indian Ocean tsunami in 2004, and the Tohoku, Japan tsunami in 2011. Tsunamis caused by earthquakes are typically long-period waves, meaning they rise and fall gradually. Depending on the geometry, size, and speed of this force, the nature of the resulting tsunami wave can vary dramatically. Tsunamis are water waves generated by a sudden force (Bourgeois 2009), typically through either rapid displacement of the seafloor (during earthquakes or from submarine landslides), or through displacement and impact (by mountain landslides entering water, glacial ice collapses, or meteorite impacts). ![]() The Taan Fiord tsunami can help us understand subaerial landslide tsunami hazards and prepare for potential impacts. Though landslides like this can happen at any time, these events are becoming more frequent-driven by climate change-induced glacial retreat and permafrost thaw. In the last century, 10 of the 14 highest tsunamis in the world were in glaciated mountains and four were in Alaska parks, which include vast tracts of glaciated terrain (Table 1). Land-slides that generate large tsunamis most often happen in landscapes with retreating glaciers. ![]() It had almost no human impacts-nobody was near enough to be harmed, and the only damage to infrastructure was rocks scattered on a beach used for landing bush planes-good fortune that may not characterize similar events in the future.Īlaska parks are prone to events like this. On October 17, 2015, 180 million tons of rock slid into Taan Fiord, an arm of Icy Bay, generating a tsunami that stripped forest from 8 square miles (20 square km) of Wrangell St.-Elias National Park and Preserve and reached as high as 633 feet (193 m) above the fjord, the fourth-highest tsunami ever recorded. A geologist stands in front of a 16-foot diameter boulder moved by the tsunami near where it reached its highest elevation (633 feet). ![]()
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