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Original Date: 30 Aug 2001 23:29:17 -0000
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Wednesday, 29 August, 2001, 00:26 GMT 01:26 UK
Giant wave devastation feared
By BBC News Online's environment correspondent Alex Kirby
An immense wave could one day wreak havoc on the eastern seaboard of
the US and elsewhere around the Atlantic.
It's entirely possible you'd see 50-metre waves coming ashore in
Florida, New York, Boston, all the way up to Greenland, and in some
cases reaching up to 10 km inland
Scientists say a volcanic eruption on the Canary Islands, off West
Africa, could trigger a vast undersea landslide.
This would set off a tsunami wave capable of inundating coastal
regions thousands of kilometres away.
But the disaster is unlikely to strike this century.
The warning comes from Dr Steven Ward, of the University of
California, US, and Dr Simon Day, of the Benfield Greig Hazard
Research Centre at University College London, UK.
Writing in Geophysical Research Letters, they refine an earlier
estimate of the likely consequences of the collapse of the western
flank of the Cumbre Vieja volcano on the island of La Palma in the
They believe a build-up of groundwater could destabilise a block of
rock up to 500 cubic km in size, which could break off in a future
eruption, rushing into the sea at up to 350 km an hour (220 mph).
The energy released by the collapse would equal the entire US
electricity consumption for six months.
The dome of water it caused would be 900 metres (2,950 feet) high, and
the resulting tsunami, higher than any in recorded history, would
travel outwards, reaching speeds of 800 km an hour (500 mph).
Waves 100 m (330 ft) from crest to trough would strike the African
coast, while north-eastwards they would affect Spain, Portugal and
France, and could still be approaching 12 m (40 ft) when they hit the
That is almost three times the maximum recorded after the Lisbon
earthquake of 1755.
Dr Day said the waves striking the UK coast would not penetrate more
than two or three kilometres inland.
But he told BBC News Online: "Weird things happen when tsunamis enter
harbours or estuaries.
"If those resonate at a certain frequency, that may substantially
increase the damage."
Across the Atlantic the damage would be far worse, with wave heights
of more than 40 m (130 ft) expected in northern Brazil.
Dr Day said: "It's entirely possible you'd see 50-m waves coming
ashore in Florida, New York, Boston, all the way up to Greenland, and
in some cases reaching up to 10 km inland.
"And that would be about nine hours or more after the initial
The ensuing economic losses would probably be in trillions of dollars,
even if there were enough warning to evacuate threatened areas and
avoid massive loss of human life.
If the speed of the landslide proved to be 150 metres per second (490
feet per second), not the 100 m/s (330 ft/s) assumed, that could
double the height of the waves reaching the US.
But Dr Day had some reassurance on the probable timescale of the
He said a collapse was unlikely this century, and perhaps for many
It could take several eruptions to destabilise the volcano enough to
dislodge the western flank, and collapse would occur only after days
or weeks of seismic activity.
He told BBC News Online: "We think you have to see some evidence of
subterranean movement before there's a risk of collapse.
"The fact that we aren't seeing any movement gives us a lot of
confidence Cumbre Vieja won't collapse spontaneously.
"But we've found that eruptions do tend to come in clusters. And
there've been two in the recent past."
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