The distant prospect of a wave of terror

If you would like to discover a potential disaster unconnected to bin Laden, let me focus your attention on La Palma, one of …

If you would like to discover a potential disaster unconnected to bin Laden, let me focus your attention on La Palma, one of the most westerly of the Canary Islands off the coast of Africa.

About a year ago, scientists decided that the western flank of a volcano on La Palma was unstable, and that some day "soon" it would collapse into the sea.

"So what!" I hear you say. La Palma, as Neville Chamberlain might very well have said, is a faraway island of whose people we know very little.

Half of the island will in any case survive, and there would still be many more Canaries left.

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But disaster for La Palma could be disaster for lots of other places, too.

If the volcano collapses, the resulting landslide will deposit several trillion tonnes of rock into the Atlantic in the space of a few minutes. This in turn could generate a series of huge tsunamis, sometimes incorrectly known as tidal waves, radiating outwards from the island to speed across the ocean faster than a jumbo jet.

A tsunami on the open sea is deceptively unobtrusive, with an amplitude of only a few feet.

As it approaches a shelving beach, however, and the depth of the water underneath decreases, the wave experiences a consequent decrease in speed.

The only way in which it can conserve its energy is to build up its height - and this it does with quite dramatic consequences.

The La Palma landslide, scientist reckon, would trigger a series of about 10 waves spaced some 60 miles apart.

As they reach the shallow water near the American coast they would build up to about 50 metres in height, enough to allow them to travel several miles inland.

The east coast of the United States and the north coast of Brazil would be the most vulnerable in such a situation, but we in Europe need not expect to come away unscathed.

The waves would radiate outward from La Palma, and be refracted by the continental shelf of western Europe, bending inwards towards the coast to cause havoc even on these islands.

But the news is not really all that bad. In seismic and volcanic terms, "soon" means sometime in the next 1,000 years.

As one of the scientists who knows about these things has put it: "These events are very rare, and shouldn't worry anyone who has a lifetime of less than one hundred years."

But, come to think of it, could it be that such an occurrence, if it happened, might not be totally unconnected with bin Laden?

Nowadays, no James Bond-style scenario is too bizarre.