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Cumbre Vieja

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Predicting Disaster: A Risky Business

24 October 2012

Predicting Disaster: A Risky Business

By Gwynne Dyer

Six years in jail and an average fine of over a million dollars: that was the punishment given to six Italian scientists on 22 October for getting their earthquake advice wrong. So what will the expert geologists and vulcanologists in Italy say the next time they are asked about the likelihood of an earthquake? They will refuse to say anything, of course.

More than 5,000 scientists have signed a letter supporting their colleagues who found themselves standing trial for manslaughter in the medieval city of L’Aquila, where 309 people died in an earthquake in 2009. But the case is a bit more complex than it first appears.

People always look for a scapegoat when disaster strikes, and it’s understandable that the bereaved people of L’Aquila wanted someone to blame. Most of them were glad when the six Italian scientists were convicted: at least somebody was being punished for the crime. But it wasn’t exactly the crime that those 5,000 foreign scientists thought they had been accused of.

Even lawyers and judges know that you cannot predict an earthquake with any certainty. What the six were actually accused of was being too reassuring about how likely an earthquake was.

There were hundreds of small shocks around L’Aquila in the weeks before the big one struck, and the six scientists were sent to the city to assess the level of danger. They judged the risk as minor, and one, foolishly, said there was “no danger”.

On the basis of this scientific advice, it is claimed, thousands of citizens decided to sleep in their houses rather than outside – and 309 of them were crushed in their houses a week later when the magnitude 6.3 quake brought them down. So the scientists’ crime was not a failure to predict the quake, but a failure to state clearly that it COULD happen.

It’s still a stupid charge. Half of the really big earthquakes are preceded by a flurry of smaller shocks, true – but such clusters of small shocks are quite common, and only 5 percent of them are followed by a major quake. So the scientists were caught on the horns of a familiar dilemma.

Fail to issue a warning before a big quake, and you will be discredited (and maybe, if you are Italian, charged with manslaughter). But issue warnings every time there is a 5 percent risk, and you will cause 19 needless mass evacuations for every necessary one. You will be “crying wolf”, which is usually counter-productive.

The scientists’s conviction will probably be reversed on appeal, bringing this whole foolish episode to an end. For the rest of us, however, this just illustrates how hard it is for human beings to deal sensibly with big but incalculable risks.

The biggest incalculable risk of a purely natural order that we know about is the mega-tsunami that will be unleashed when the western flank of Cumbre Vieja volcano on the island of La Palma in the Canaries slides into the Atlantic Ocean. In an eruption in 1949, a chunk of rock about 500 cubic km. (120 cubic miles) in size, with a mass of 150 billion tonnes, became detached from the main ridge and slid two metres (7 ft.) down towards the sea.

This is bad news for people living around the Atlantic Ocean. In some future volcanic eruption (there have been six in the past 500 years), that whole mass may slide all the way into the ocean and generate a tsunami that would initially be about 600 metres (2,000 ft.) high.

It would travel outwards in an expanding circle at some 1,000 km. per hour (600 mph), destroying everything on the western coast of Africa in one hour. It would inundate England’s south coast in three, and reach the east coast of the United States, Canada iand Cuba in six. Brazilians would have to wait a little longer. The waves would reach up to 20 km. (13 mi.) inland in low-lying areas. Many tens of millions would die.

So let’s imagine that there’s another eruption on Cumbre Vieja, and a committee of global experts is convened to watch the western flank for signs of movement. Should they advise evacuation along all the vulnerable coasts? That’s several hundred million people. Who will give those people food and shelter? How long must they stay inland? And the economic damage would be huge.

The experts can’t wait until the last minute to give their advice: you can’t evacuate the entire US east coast in six hours. If they advise evacuation, and nothing bad happens, they will be the most unpopular people on the planet. If they don’t, and the worst does happen, they will be seen as guilty of mass manslaughter, just like the Italian scientists at L’Aquila.

Since it will always be much likelier that no catastrophe is going to happen this time, the experts will almost certainly issue reassuring statements intended to keep people in their homes. Just like the Italian scientists. And yet some day, next week or a thousand years from now, that mass of rock on Cumbre Vieja will really fall into the sea. Damned if you do, and damned if you don’t.

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To shorten to 725 words, omit paragraphs 3, 4 and 9. (“People…was”, and “The scientists’…risk”)

 

 

With a Little Warning

3 January 2005

With a Little Warning…

By Gwynne Dyer

“We may have severely underestimated the level of the tsunami hazard along the margins of the Atlantic Ocean,” said an unnamed researcher at the Benfield Hazard Research Centre at University College London (quoted in the Financial Times of 2 January). Scientists do jump on the bandwagon at times like these, but you can hardly blame them; it’s the only time they can really get our attention..

By the end of this year, the countries of South Asia will almost certainly agree to install a system to give advance warning of tsunamis like the one that killed an estimated 150,000 people on 26 December. A similar system has been operated by the countries around the Pacific Ocean since 1968, and one could be installed around the Indian Ocean for about $10 million, although individual countries would then have to spend further amounts to get warnings to their people who live in low-lying coastal areas in a timely fashion.

Such a system wouldn’t have saved many people in northern Sumatra, where the tsunami struck within half an hour of the massive earthquake (at 9.0 on the Richter scale, the biggest in forty years) that occurred just off the west coast. But it would have given people in Thailand and Malaysia over an hour to get to higher ground, and well over two hours in Sri Lanka and India.

The property damage would have been the same, and 5 or 6 million people would still be homeless, but even this time as many as 50,000 lives could have been saved by a proper warning system. Another time, when the undersea quake didn’t happen so close to a densely populated coast, the great majority of the lives at risk might be saved — so why is no system in place? Basically, because big earthquakes are very rare in the Indian Ocean.

The Pacific Tsunami Warning System has been in business for almost forty years because the Pacific rim — the “ring of fire” — has over half the active volcanoes and eartyhquakes on the planet, and an average of ten tsunamis a year. No quake has caused a big tsunami in the Indian Ocean since Krakatoa exploded in 1883, and human beings don’t readily respond to merely theoretical dangers.

Which brings us to the Atlantic, an area of even less seismic activity. The last subsea earthquake big enough to cause a tsunami in the Atlantic was the great Lisbon quake of 1755, whose 60,000 victims included tens of thousands killed by the tsunami that struck the city only minutes after the original shock-waves. But there is another problem in the Atlantic — La Palma, in the Canary Islands.

It was Dr Simon Day of UCL’ s Benfield Hazard Research Centre, in cooperation with the Swiss Federal Institute of Technology in Zurich, who modelled what will happen when one day, probably during a volcanic eruption, Cumbre Vieja, the western half of La Palma, falls into the sea. Five hundred cubic kilometres of rock (125 cubic miles) weighs about 500 billion tonnes, and when it plunges into the ocean, the model predicts, it will cause a mega-tsunami. It will be 650 metres (half a mile) high in the Canaries themselves, and still “several tens of metres high” — say fifty feet — when it strikes the east coasts of the United States, Canada, Cuba and Brazil eight to ten hours later.

“There’s no “if” about it,” says geophysicist Dr Bill McGuire, also of the Benfield Centre. “It will happen; it’s just a question of time.” But although La Palma is the most volcanically active in the entire Atlantic region, it could still be quite a lot of time before Cumbre Vieja falls off.

The volcano has erupted in 1470, 1585, 1646, 1677, 1712, 1949 — that was when the whole western side of La Palma slid down four metres (thirteen feet), alerting the scientists — and most recently in 1971. It has probably been erupting every century since long before people started recording it. Yet Dr Day estimates that there is only a five percent chance that Cumbre Vieja will collapse in any given century — so what do you do if the volcano erupts again?

You certainly don’t evacuate the whole east coast of North America, most of the Caribbean and northeastern South America, plus all the coastal areas from Guinea to Morocco in West Africa and from Spain to Ireland in Europe. You can’t make hundreds of millions of people refugees for months or years and cripple entire national economies just because a volcano is erupting in La Palma and there’s a five percent chance of disaster. But a warning system that gave people a decent chance of survival if the worst happened would certainly help..

For many coastal areas, a couple of hours’ warning of a tsunami is all that would be needed for people to make it to higher ground. For some large coastal cities where traffic bottlenecks prevent rapid evacuation, refuges in the upper stories of tall building that can withstand a tsunami might be needed, but nothing too expensive or elaborate. We are talking about human nature here, and against a low-probability catastrophe, people will only pay for low-cost insurance .

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To shorten to 725 words, omit paragraphs 3 and 4. (“Such…Ocean”)

Unstoppable Gee-Gees

11 August 2004

Unstoppable Gee-Gees

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.

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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To shorten to 725 words, omit paragraphs 6 and 9. (“They’re…print”; and “They…years”)PLEASE NOTE: I SHALL BE USING DOUBLE QUOTATION MARKS IN ALL CASES FROM NOW ON, AS SINGLE QUOTATION MARKS TEND TO VANISH IN ALMOST EVERY E-MAIL PROGRAM KNOWN TO MAN. YOU ARE FREE TO TURN THEM BACK INTO SINGLE QUOTES WHERE APPROPRIATE

Catastrophes

5 February 2004

Catastrophes, Calamities and Cultural Lag

By Gwynne Dyer

Now we have to worry about gamma rays, too. University of Kansas astrophysicist Adrian Melott told the annual meeting of the American Astronomical Society last month that the Ordovician extinction, which wiped out most of the species on Earth 440 million years ago, was probably caused by a huge burst of gamma rays from outer space. A giant star around 10,000 light years from here exploded, and when the resulting gamma rays struck our planet they destroyed the ozone layer and created a toxic brown smog that cut the sunlight reaching the surface in half. Over two-thirds of the species that then existed became extinct. Oh, and you can expect another such event every few hundred million years.

“It could happen tomorrow or it could be millions of years,” said Dr. Melott. Just to be safe, though, maybe we should build a giant screen to shield the Earth from gamma rays. We’d have to dismantle Mars to get enough material, of course, and it would be tricky to move the screen round to the right side of our planet fast enough when we see an exploding star somewhere. And since the gamma rays would arrive at exactly the same moment as the first visible light from the explosion, we wouldn’t have any warning time at all….

Perhaps we should just hope it doesn’t happen again any time soon, since there is actually nothing we can do about bursts of gamma rays. But the past twenty years or so have seen a whole series of discoveries about abrupt and catastrophic events that have hugely affected life on Earth in the past, and some of them are neither unpredictable nor unstoppable. Take asteroids, for example.

Most people know that it was a giant asteroid smashing into the Gulf of Mexico that killed off the dinosaurs 65 million years ago, making way for the age of the mammals. Fewer people know that it was probably another asteroid, smashing into what is now eastern Quebec around 200 million years ago, that opened the way for the dinosaurs. It was one of the less dramatic extinction events, killing off only half the species on Earth, but it did eliminate the mammal-like reptiles that were then the dinosaurs’ major competition.

“Dinosaurs skated through this, but large mammal-like reptiles went completely extinct,” explained paleontologist Peter Ward of the University of Washington in 2001. “One of the great mysteries has been…why would these creatures, which are seemingly better adapted for eating a variety of plant sources, die out and the dinosaurs not? And the answer is: mass extinctions don’t give a hoot about your adaptations for everyday life. There’s a lottery involved.”

At least 900 asteroids more than half a mile (1 km.) in diameter cross the Earth’s orbit. Small but still potentially dangerous asteroids hit our planet all the time: one that struck north of Lake Baikal in eastern Siberia in September 2002 flattened 40 sq. mi. (100 sq. km.) of forest. (If it had come down over Moscow or New York, it would have killed millions.) So you would think that human beings would be trying hard to create a defence against this danger, would you not?

“If we’re due to be hit within a day, week, month or year, we’re not going to spot it,” said astrophysicist Duncan Steel of Salford University. “A 200-metre object plonking down into the Atlantic would effectively take out all the cities around the seaboards. Those smaller events occur rather more frequently — (it’s a) once every several thousand years event.” Steel believes, however, that this sort of disaster can be prevented: “If one’s due in 50 years, I think we could spot it….I’m optimistic that we have the scientific and technical capability to detect and divert it.”

Good luck, but there is already a well-known object — much slower-moving but vastly more massive — that could produce a tsunami big enough to drown all the cities that face the Atlantic, and nobody is even watching it. An enormous chunk of the Cumbre Vieja volcano on the island of La Palma in the Canaries has become detached from the main body of the island and is sliding slowly towards the sea. It suddenly dropped more than 4 yards (4 metres) in 1949 and then stopped, but it continues to creep seaward.

If it drops into the sea one day, a tsunami 60 yards (50 metres) high will reach the west coasts of Africa and Europe in an hour or two, and the east-coast cities of the United States in four hours. A few hours’ warning could save millions of lives, so you probably think that somebody is monitoring the movement of this mass of rock. Wrong. The people who have most to lose if Cumbre Vieja slides into the sea are paying no attention at all.

We are also paying little attention to global warming, and failing to monitor 90 percent of the world’s 3,000 volcanoes even though a really big once-in-50,000-years explosion would cause the equivalent of a nuclear winter. (There’s nothing you can do about a supervolcano exploding, but at least you can have a few years’ warning to prepare.) It’s a kind of cultural lag. We have discovered that our world is a far more dangerous place than we ever dreamed, but we still can’t accept the reality of it.

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To shorten to 725 words, omit paragraphs 2 and 5. (It could…all; and”Dinosaurs….lottery”)