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Yes, Atlantic Tsunamis Do Happen

A lot of people know that New York City sits on fault lines (and that the Indian Point Nuclear Power plant is above the intersection of two active seismic zones), all of which makes it entirely possible that the city could suffer a catastrophic earthquake. But I thought at least I and my fellow citizens didn't have to worry about tsunamis. Turns out that might be wrong, according to Viable Opposition.

Viable Opposition is a geoscientist, and he either remembered or dug up this paper (pdf) by Steven N. Ward and Simon Day, published in Geophysical Research Letters in 2001. It describes how the Cumbre Vieja volcano in the Canary Islands might lose its western flank in an eruption, dropping an immense amount of material down to the sea floor and sending a tsunami across the entire Atlantic. Their worst-case scenario is wave heights in Florida of 80 or so feet; somewhat earlier, Newfoundland would get a still very noticeable 30-foot tidal wave. They don't mention New York City. That's fine by this resident; I don't want to think about it.

I'm not sure we should decide that the threat is a settled fact, as V.O. seems to have. Another geophysicist, George Pararas-Carayannis, later examined the Ward and Day study and decided that they'd greatly overstated the risk and "created unnecessary anxiety." And I wondered why, if this kind of thing can happen in the Atlantic, we have no historical records of this sort of disaster. [UPDATE: That was a pretty dumb thing to wonder, I learned from commenters Textículos Selvagens and Richard Smith. The Lisbon earthquake of 1755 was followed by a devastating tsunami. And geologists have evidence of colossal pre-historic tsunamis caused by massive landslides in what is now Norway. I stand corrected, and I've changed this post's title accordingly.]

In any event, anxieties today would be better spent focussed on helping those who are suffering and wondering, as V.O. does, about the seismic safety of American nuclear plants. Nonetheless, it's good to be reminded that prediction, as Niels Bohr said, is difficult, especially when it involves the future.

Ward, S., & Day, S. (2001). Cumbre Vieja Volcano—Potential collapse and tsunami at La Palma, Canary Islands Geophysical Research Letters, 28 (17) DOI: 10.1029/2001GL013110

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