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Giant Waves May Endanger Atlantic
The giant waves called tsunamis, long known
as a danger in the
Pacific Ocean, may also pose a danger to the
U.S. East Coast.
Published on August 28 2001
WASHINGTON (AP) - While stressing that
there is no indication it could happen soon, a pair of
scientists is warning that a slumbering volcano on the island of
La Palma, off the coast of Africa, could one day give way in a
massive landslide, sending waves up to 70 feet high crashing
into Florida and other coastal states.
The volcano, Cumbre Vieja, last erupted in 1949. It has not
shown any recent activity.
But one day a new eruption could cause an existing rift across
the volcano to split open, sending a landslide crashing into the
ocean, say geophysicists Steven N. Ward of the University of
California at Santa Cruz and Simon Day of University College,
London.
In what they said was a worst-case scenario, a wave nearly
70-feet high could strike parts of the East Coast in only nine
hours. Giant waves also could slam into Africa and northeast
South America.
Ward stressed that a wave that size is unlikely, and that
smaller landslides would produce waves one-fourth to half that
height.
``Let's not scare people,'' Ward said. ``Certainly there is no
indication that this will happen anytime soon.
``Even when there is an eruption, the probability of collapse is
low,'' Day said. ``There may be many eruptions before the
volcano is finally weak enough to collapse.''
Peter Lipman, a volcanologist with the U.S. Geological Survey in
Menlo Park, Calif., agreed that the threat exists from the
volcano. He, too, was cautious about when such a disaster might
occur.
``These oceanic island volcanoes are, in geologic time, very
subject to exactly the kind of process they describe,'' he said.
``Volcanoes try to keep on adding lava to a steep slope and
eventually they get the slope so loaded that it fails.
``I don't see this as something that is likely to happen very
often at La Palma,'' he said. ``But it had a failure like this
half a million years ago and will again in the future.''
Ward and Day's findings are reported in the Sept. 1 issue of
Geophysical Research Letters.
Tsunamis (soo-NAHM-ee), long have been known as a danger around
the Pacific Ocean, where warning centers monitor the sea and
alert coastal residents. They are most often generated by
earthquakes or landslides under the sea and are occasionally,
incorrectly, referred to as tidal waves.
The waves have not received much attention as a hazard in the
Atlantic. The most recent tsunami on the East Coast occurred in
1929 when a landslide off Newfoundland created a large wave that
killed 30 people in Nova Scotia, Day said.
Unlike surface waves, tsunamis reach all the way to the sea
floor. In mid-ocean they may hardly be noticeable, but as they
approach shore the sea floor rises and so does the wave above
it, potentially rising to giant status. And they travel very
fast.
The worst case scenario Ward and Day describe in their paper
runs like this: Within five minutes of the collapse, a wave
1,500 feet high has zoomed 30 miles out to sea; at 10 minutes,
it is down to 900 feet and slamming into nearby islands. After
six or more hours, waves of 30 feet or so arrive at Newfoundland
and at about nine hours, the East Coast of the United States is
hit by waves ranging from 30 feet to 70 feet.
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