11 August 2004
By Gwynne Dyer
The western flank of Cumbre Vieja volcano on the island of La Palma in the Canaries is going to slide into the Atlantic one of these days: a diagonal fracture has already separated it from the main body of the volcano, and only friction still keeps it attached. "When it goes, it will likely collapse in about 90 seconds," said Professor Bill McGuire, director of the Benfield Grieg Hazard Research Centre at University College London. And when it goes, probably during an eruption, the splash will create a
mega-tsunami that races across the Atlantic and drowns the facing coastlines.
Fortunately the nearest coast to the Canary Islands, where the waves will be around 300 feet (100 metres) high when they hit, is lightly populated Western Sahara. Few people living in the coastal plains of Morocco, south-western Spain and Portugal will survive either, but the waves will drop in height as they travel. The coasts of southern Ireland and south-western England will also take a beating, but by then the wave height will be down to about 30 feet (10 metres).
The real carnage will be on the western side of the Atlantic, from Newfoundland all the way down the east coast of Canada and the United States to Cuba, Hispaniola, the Lesser Antilles and north-eastern Brazil. With a clear run across the Atlantic, the wall of water will still be between 60 and 150 feet (20 and 50 metres) high when it hits the eastern seaboard of North America, and it will keep coming for ten to fifteen minutes.It will take the wave about 9 hours to cross the Atlantic to reach Canada.
Worst hit will be harbours and estuaries that funnel the waves inland: goodbye Halifax, Boston, New York, Philadelphia, Baltimore and Washington, DC. Miami and Havana go under almost entirely, as do low-lying islands like the Bahamas and Barbados. Likely death toll, if there is no mass evacuation beforehand? A hundred million people, give or take fifty million.
The last time the volcano erupted, in 1949, its whole western side slid 13 feet (4 metres) down towards the sea, and even now it is still slipping very slowly downwards. Given the scale of the catastrophe if the next eruption sends this mountain crashing into the water, Dr. McGuire is angry that there is so little monitoring equipment on La Palma to give advance warning: "The US government must be aware of the La Palma threat.
They should certainly be worried, and so should the island states in the Caribbean that will really bear the brunt of a collapse."
"They're not taking it seriously," McGuire concluded. "Governments change every four or five years and generally they're not interested in these things." It was a classic scene, revisited in every natural disaster movie: crusading scientist calls feckless governments to account, squalid politicos ignore the call. The science journalists couldn't wait to get their pieces into print.
But hold on a minute. Haven't we heard about this threat before? What's new this time? Nothing, except that there hasn't been a stampede to cover La Palma with seismometers. Now, why do you think that is?
Suppose that the governments whose coastlines are at risk, from Morocco to the US, did get a warning that Cumbre Vieja was waking up again. What would they do with the warning? Evacuate one or two hundred million people from the low-lying lands indefinitely?
They don't know if there is really going to be an eruption
(seismology is not that precise), or how big it will be, or whether this will be the one that finally shakes the side of the mountain loose. It could happen in the next eruption, but it might not happen for a thousand years.
No national leader wants to evacuate the entire coast for an
indefinite period of time, causing an economic and refugee crisis on the scale of a world war, for what might be a false alarm. But nobody wants to ignore a warning, and perhaps be responsible for tens of millions of deaths. From a political standpoint, it's better not to have the warning at all.
Natural disasters that can affect the whole planet are known to scientists as "global geophysical events" -- gee-gees, for short -- and they come in two kinds: ones you might be able to do something useful about, and ones you can't. When governments are faced with the first kind, they can respond quite sensibly.
Since we first realised two decades ago that asteroids and comets smashing into the earth have caused a number of mass extinctions, a US government project has identified and started to track 3,000 "near-earth objects" whose orbits make them potentially dangerous. In another generation, we may even be able to divert ones that are on a collision course -- and if there's one gee-gee that you would want to prevent above all others, that's the one. But there's no similar remedy on the horizon
for volcanos or earthquakes, or the tsunamis they might cause. On this one, we just have to keep our fingers crossed.
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