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Swept Away

Imagine being in the position to receive this (fortunately quite fictional) report:

President's Daily Brief Date: May 7, 2008


Seismologists have detected an increased amount of seismic activity on the island of La Palma in the eastern Atlantic ocean. The USGS believes that this is the first warning of an imminent collapse of its north-western landmass. This will trigger a "mega-tsunami" of approximately 60-150 feet in height, traveling at approximately 560 miles per hour, continuing for approximately 15 minutes, hitting the entire length of the continental United States eastern coastline. The entire east coast will be flooded for fifty to one hundred miles inland, depending upon elevation. Port cities will be hardest hit, as harbors will channel the wave. We will have nine to twelve hours between the collapse of La Palma and the initial arrival of the mega-tsunami on the American coast, an insufficient time to evacuate the approximately 100 million citizens who will be affected by the disaster.

USGS estimates the likelihood of La Palma collapse within the next two weeks to be 35%, increasing to a 75% chance by 2016.

If that bit of terriblisma sounds like the pitch for a particularly silly science fiction movie, think again. The only imaginary numbers in that scenario are the date and the estimated chances. La Palma, part of the Canary Islands off of Africa, is very likely to collapse during a violent seismic event -- and given that La Palma is volcanic, seismic events are not unknown -- dumping a chunk of rock the size of a mountain into the Atlantic ocean, triggering a massive tsunami. The west coast of Africa would be hit by a 300 foot swell, while the eastern coastlines of North, Central, and South America would be hit by a somewhat smaller -- but still utterly devastating -- inundation.

(The collapse of La Palma was started by an eruption of its volcano in 1949, and the next volcanic event could possibly -- but not certainly -- finish the job. Eruptions of La Palma are sporadic; the most recent one was in 1971, but the last one prior to 1949 was in 1712. The 2001 study of the geophysics of La Palma which first alerted people to this possibility is available here (PDF), and a summary is here.)

Even moreso than an asteroid impact, this is one of those very possible wild cards that is nearly impossible to wrap one's head around. Earthquake in the Canaries, and nine hours later, whoosh! Everything from Rio to Nova Scotia is under 50+ feet of water. There's very little that could be done to stop such an event from happening -- we couldn't build a barrier strong enough to resist such a swell, and dismantling the rock is a formidable challenge at best and might itself trigger the collapse. The effects of such a disaster are almost unimaginable.

What we can better imagine, though, are the choices facing researchers and global leaders. Right now, there are few seismic sensors on La Palma -- we are unable to get any real warnings of imminent collapse. Putting in sensors could give an early warning of a possible disaster, but such an alert would put leaders in the position of needing to decide whether to evacuate at-risk areas, knowing full well that seismic warnings are inexact, and the actual collapse could still be years -- even decades -- off. Leaving La Palma without seismic sensors, conversely, would make it impossible to be wrong, but could doom millions of people when the island eventually does collapse -- whenever that actually happens. It's not an easy choice.

Knowledge that such a disaster is not just possible, but perhaps inevitable, is one of the side-effects of our increasingly better understanding of the Earth's physical systems. In centuries past, a disaster such as this would have taken us all by surprise, and maybe even resulted in new mythologies (such as how the Mediterranean breaking through the Bosporus and creating the Black Sea may have been the source for the various flood myths of the Asia Minor religions). Today, the potential for such a disaster is a cause for concern, a spur for better understanding of seismology, and a reminder that we are not masters of this planet, but temporary residents.

My question for the readers, then, is: if you were President (insert Prime Minister, Governor, etc., as desired), what would you do about the inevitable -- but possibly far-off -- collapse of La Palma?


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Comments (10)


While a structure to outright block a wave of that size is of course not possible to build with current technology, it *may* be possible to mitigate the effects with smaller structures. This is not an uncommon somution for smaller waves in some areas. As president, I would divert funding into researching this.

Also, since it is a wave, there may be the possibility of creating a series of artificial interfering waves to lessen the impact. Done correctly, with the interference maximized when the waves cross, this may form "safer" spots in the wave front. This would require research funding as well.

Unfortunately the only things we have powerful enough to create waves of a magnitude that would have a chance of meaningful interference are nuclear weapons. On the plus side, we have plenty of those, on a half-hour flight time to anywhere in the world.

I can't believe how surreal that last sentence is.


    Well to answer the question as President I’d do nothing. As President of the US this is a purely political calculation. The chances of such a failure happening in the next eight years are very, very small and spending any political capital on an island that the most of the electorate has never heard of would be silly. The risk of being mocked by the other party is simple too great for such a small potential payoff and any political advisor who says otherwise should be fired. I'm not sure how the political calculus breaks down for Governors or Prime Ministers, but for President it's a no brainer.

    Now as an Engineer it's a much more interesting problem. The big issue with La Palma is that vertical stands of impermeable rock are holding large amounts of rainwater inside the volcano. This water provides both outward pressure pushing on the layers of the mountain and lubrication to help great sheets of rock fall off into the ocean. So draining the water through sideways bored tunnels along with sealing the top to keep more rain water from entering would be a good start. Then add concrete filled dilled holes to stabilize things before using traditional blasting techniques to take apart the mountain in pieces. Probably a several billion dollar project not helped by being in the middle of nowhere, but it's doable.


Interesting suggestion. The only potentially large problem with it that I see is that releasing the core water pressure might have unpredictable effects on the rock around it. If it could be somehow forced to fall onto land if it breaks up, that would be ok, even if it slid into the sea later. But if it caused cracking of the rock due to pressure changes it may weaken it enough to prematurely cause the event. Hard to say without a lot of calculation.


La Palma is inhabited and has cultural and economic activity. Destroying the mountain just to remove the risk would mean destroying all that activity with very little political justification.

That's why a crafty politician would need to address the UN about this issue, creating a multilateral risk assessment organization for cataclysmic natural disasters. This organization could issue recommendations which the US could subsequently ignore (I'm so cynical), but which would raise awareness along the right lines.

Preventative engineering would likely never happen, and the only real effect would be to give organizations like FEMA some extra data on which to base their contingency plans.


As president I would make sure all my opponents were on that side of the country facing it;/

As a normal person I would just make sure I was on the other side;/

Zaid Hassan:

Ignore it. We all gotta die someday.

Might as well focus our energies on the huge list of things we know we can do, with what we have today.

But Z, that attitude -- "ignore it, we all gotta die someday" -- could well be applied to any number of problems which you may personally feel are more important. The Palestinian-Israeli conflict, maybe: they just keep killing each other, no matter what anyone says or does, so just ignore 'em. Or global warming: climate change happens, we had a good run, ignore it. How many people should we be willing to write off because the problem doesn't have an immediate solution?

Besides, problem solving is not a zero-sum game. I would expect that the kinds of cooperation, foresight, emergency planning, and geophysical system understanding required to deal with this extreme possibility could have myriad spin-off benefits for other, less disastrous (and more immediate) problems.

Ultimately, it's a thought experiment. I really doubt that any nation is going to devote tons of resources to solving the La Palma threat, but it certainly doesn't hurt us to imagine how such a problem might be resolved.

Zaid Hassan:

Personally I think it's a relatively useful attitude to take :-)

We live in a culture where what we do in the present is subservient to the imaginary future, where we spend more skull sweat on preventing things from happening to us out of fear - than in living in the present with the knowledge that you can't minimise the randomness of the universe. It will find you no matter where you hide.

One of my issues with "future" thinking is that it ignores the many, many things we can do in the present with what we already know. I find it odd that we talk about "another world is here" and then lunge off into thought experiments about the future.

Certain classes of problems are largely a waste of time and energy - particularly when we'll dealing with issues that are hypothetical and purely precuationary. It's a little bit like worrying about a hypothetical illness while your arm is stuck in a moving elevator. Get your arm out first and then worry about the damned asteroid strike.

There is a big difference between the Israeli-Palestine problem and a potential asteroid strike on earth. Surely you can see that these two problems are of different classes?


One is intractable and dependant upon reconciling the whims of people that hate each other, while one is a theoretical problem that might be approached before it becomes a done deal?

Unfortunately the Spanish Govt have stopped funding the Benfield Hazard Research Centre (the guys who have been keeping an eye on the Cumbre Vieja). At the moment there are only three siesmographs on the site and they are around 4-5 years old. What they need are GPS systems to monitor the fracture to track its movements, along with satellite imagery to see if some parts are moving faster than others, which would cost around US$50,000. If I were President, I'd be funding it and setting up contingency plans on how deal with evacuating the east coast in 8 hours. I have no idea why the Spanish Govt stopped funding it and why no other research institute or government hasn't offered to help out. The threat is real.


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