Volcano watch: The Canary Islands “mega-tsunami” hypothesis, and why it doesn’t carry water

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Maui Now

The recent eruption on La Palma, in the Canary Islands, has stimulated speculation that the volcano might collapse, creating a tsunami that would devastate the east coast of North and South America. But is such a scenario possible or likely?

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The Canary Islands “mega-tsunami” scenario assumed a single, coherent, massive collapse block that reached a high velocity very quickly. Ocean floor mapping surrounding the Canary Islands, however, indicates that collapses instead occur in incremental or piecemeal fashion. In addition, geomorphologists found, via slope stability analysis, that the potential collapse volume is much smaller than was simulated by the 2001 paper.

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These new simulations suggest that the maximum wave height along the east coast of the Americas from a “worst-case scenario” collapse of La Palma would be on the order of 1-2 m (3-7 feet)—still hazardous, but similar to common storm surge.

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Collapses of Canary Island volcanoes are rare, occurring on timescales of hundreds of thousands of years, and should be preceded by signs of flank instability: increases in earthquakes and ground surface deformation. Canary Island volcanoes also erupt regularly—La Palma last erupted in 1971 and 1949—and slope stability analyses conducted at La Palma indicate that the structure is stable. The volcano would have to grow significantly before a collapse was likely.

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