Mega-tsunami

From NewScientist:

Mega-tsunami will devastate all Atlantic coasts
When half a Spanish island collapses, tsunamis will devastate the coastline of countries all around the Atlantic - all because tsunamis can turn corners.
Last year, Simon Day of University College London and his colleagues reported that a flank of a volcano on the island of La Palma in the Canary Islands was unstable (New Scientist, 7th October 2000, p 26).
If the flank collapses, which Day expects to happen sometime in the next few thousand years, the resulting landslide will dump a trillion tonnes of rock into the Atlantic within minutes. Day predicted that this would probably send a huge tsunami raging towards America's East Coast.
Now he has teamed up with Steven Ward, a wave expert at the University of California, Berkeley, to work out the tsunami's size and spread. Ward has developed a model of waves triggered by underwater earthquakes, ranging from a mere eight centimetres high for a magnitude-6.5 earthquake, to tsunamis several metres high for a real whopper.

Caving in
When the La Palma volcano caves in, Ward says it will trigger a series of around ten waves, spaced about a hundred kilometres apart. As they reach the shallow water near the North American coast, they will build up to about 50 metres high, enough to travel several kilometres inland. "There's a significantly broad danger zone," says Day.
Although the volcano's unstable flank points directly towards North America, it is not just North Americans who should be worried. Day originally estimated that the collapse would create a shockwave travelling in a straight line across the Atlantic, directly towards America's East Coast. This would happen if the speed of the landslide was faster than the speed of the waves in deep water.
But the model shows that the landslide will actually move at around 100 metres per second, about two-thirds as fast as the waves in the water. This means the tsunamis will spread out in an arc.
Shallower water near La Palma would then slow the waves down, forcing them to curl around towards northern Africa and northern Europe, even behind La Palma on the Spanish coast.

Rare events
Gary McMurty, who works on landslides at the University of Hawaii, says there is no point losing sleep just yet. "These events are very rare and shouldn't worry anyone who has a lifetime of less than a hundred years," he says.
But even if beach bums can rest easy, Day expects the result to shake up geologists. Now they know that tsunamis can spread out and turn corners, he hopes researchers will be more flexible in matching inland deposits of shells, coral and sand to ancient landslides on distant continents.
"Northern Brazil is going to be a good place to look for past evidence of collapses at the Canaries," says Day. "We wouldn't have thought of that."

 

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i've heard it's happened to the areas now known as hawaii several times in the last few million years - and will undoubtedly happen again - with devastating consequences to the west coast.

- js.

 

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yup...

 

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Iv'e heard about this threat in the Canary islands. I don't know how bad it would be though. Even if billions of tons of water are displaced, if it were stretched over the entire atlantic coast of europe and the americas. The huge tsunami could then be diluted down to no more than a large wave.
As with a lot of these scares the people looking at this island need more money to fund thier projects. The best way to get money is to create a scare and even if it was true there is nothing we could do.
If you believed them all you would would find it impossible to find a safe place to live.

 

I think you may be quite safe in Essex for a while yet!

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I wouldn't bother relaxing until you've read up on the subject. There's a lot of credible physics behind the theory. Sadly, it's not just America that'll be whacked (as the original article suggested); later modelling revealed that Europe would indeed be affected. Pity, really; it'd be a good idea otherwise for anyone with a spare bulldozer and volcano.

 

Its impossible to be safe in Essex.

 

Holy 10 year old thread Batman.