This idea was hotly debated at the time the paper was published, the argument against being that a La Palma collapse would be a series of landslides rather than a single mass of rock i.e. the difference between dropping a brick in your bathtub or gravel of the same weight.
Here's The New Yorker:
The chances are slim that any of us living in New York will ever experience a destructive tsunami like the one that struck Japan last week. But if a tsunami were to hit New York, Steven Ward, a professor at the University of California Santa Cruz's Institute of Geophysics and Planetary Physics, would be one of the only people who could say, "I told you so." (Although that would be kind of inappropriate.) Ward and his co-author, Simon Day of University College London, released a paper in 2001 detailing the possibility of a tsunami hitting New York — and the entire eastern coast of the United States — at some point in the future. Unlike the Japanese tsunami, this one would be set off by an eruption of the Cumbre Vieja Volcano in the Canary Islands off the coast of Africa. When this happens, the volcano will "experience a catastrophic failure of its west flank, dropping 150 to 500 km³ of rock into the sea," which, if you're wondering, is a lot of rock. Ward sets the scene: "You remember Mt. St. Helens? Well that was pretty exciting, and that was 5 km³, so this could be 100x larger. Put it in the water, and it'll be a big event when it happens."A more realistic threat:
The size of the resulting tsunami will depend on how large the landslide actually turns out to be, and whether it happens quickly or in phases. Ward created a video showing the flooding that would occur in New York, nine or ten hours after the collapse, based on a twenty-meter wave, which is in the middle range of what's possible. As you can see, wide swaths of Manhattan, Brooklyn, Long Island, New Jersey, and Staten Island would be underwater....MORE
Could a big earthquake reduce Manhattan to rubble someday?
I'll get to the odds of a hurricane wiping out the Jersey Shore gang as we get closer to the hurricane season.