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> Tsunamis Can Happen Across the Globe, Experts Warn; 2005
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| Tsunamis Can Happen Across the Globe, Experts Warn; 2005 |
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| by RANDY LEE LOFTIS |
The death toll in Southeast Asia may have reinforced a widespread but dead-wrong belief: that tsunamis happen only when earthquakes strike in faraway seas. Sudden, devastating waves can happen around the globe, even where the risk of a major earthquake is small, experts warn - including the United States' densely populated Atlantic coast and along Texas' coast on the Gulf of Mexico.
Neither coast has a tsunami warning system, and Texas' state emergency plans don't mention tsunami risks because the chances of one occurring seem small. People in the most earthquake-prone states - Alaska, Hawaii, Washington, Oregon and California - know from experience how destructive the twin threats of quakes and tsunamis can be. But the tsunamis that might threaten the Atlantic or gulf coasts might not come from earthquakes. In the Atlantic, a grave threat in addition to distant earthquakes is the collapse of a volcano across the ocean.
Volcano-induced tsunamis, which occur when huge amounts of heaped-up volcanic material slide into the sea, have occurred innumerable times with local effects. But one will happen with catastrophic impact, scientists believe, during a future eruption of a big volcano such as Cumbre Vieja in the Canary Islands off of northwestern Africa.
The tsunami from the predicted collapse of Cumbre Vieja, fanning out across the Atlantic at about 500 mph, would drown Florida within nine hours with waves from 33 to 82 feet high, according to a 2001 estimate by scientists at the University of California and London's University College. That's enough to put nearly all of Florida under water and damage the whole country's Atlantic coastline. In the Gulf of Mexico, the risk isn't from earthquakes or volcanoes, but from another little-known source: underwater landslides that generate huge waves. It's not a theoretical threat to the Texas coast; it's already happened.
An undersea landslide - technically, a "slump" - about 90 miles off Galveston once sent some 12 to 14 cubic miles of earth sliding down. The slump at the gulf's East Breaks formation threw a tsunami estimated at 25 feet high onto the Texas shoreline, according to researchers who have studied its geological aftermath on the gulf floor. That was about 5,000 to 10,000 years ago - many lifetimes for humans, but a blink in geological time. Peter Trabant, a marine hazards consultant in Houston who has studied the landslide, said there's no reason to believe that it won't happen again. "If it happened again, it would rush over all the barrier islands, including Galveston Island, and all the coastal cities - Port Arthur, Galveston, Freeport, Corpus Christi," Trabant said. "There's definitely a possibility that this could happen at any time." Still, the likelihood that it will happen anytime soon seems so small that Texas has done nothing to plan for it.
Texas' official emergency plans, which deal in detail with hurricanes, tornadoes, floods, fires and a host of other natural or human-induced catastrophes, don't mention tsunamis, said William Ayres, spokesman for the state Division of Emergency Management. If a tsunami threatened the Texas coast, Ayres said, officials would use the warning and evacuation plans already in place for hurricanes to get people out of harm's way.
That's a problem, however. Emergency planners can track a hurricane for days. Even an earthquake- or volcano-induced tsunami can allow for hours to get people away from the most dangerous areas. But a landslide-induced tsunami might offer no warning at all. Earthquake monitoring systems wouldn't pick it up, experts say. So the first time the public knows about the tsunami might be when it slams into the shore. "You can't detect them," said Harry Woodworth, a meteorologist with the National Weather Service. "You don't have much time to react."
Woodworth, who works in the weather service office in Mount Holly, N.J., has gathered historical records on landslide-induced tsunamis in the Atlantic. He said the Indian Ocean disaster had dramatically boosted public interest in his research. But a warning system for currently unprotected areas of the United States is still a long way off. Woodworth has a practical suggestion in the meantime: Train lifeguards to recognize the sudden rise or fall in sea level that would signal an oncoming tsunami. "It might give enough time to get people out of the water and off the beach, at least," he said.
Two tsunami warning systems run by the U.S. government try to protect people in Alaska and the eastern Pacific, while another, operated by Japan, issues warnings for the western Pacific. No such system exists for the Indian Ocean, site of last week's disaster. The United Nations said last week that it would press to have one in place within a year.
Big earthquakes are relatively rare in the Atlantic, which does not experience the same level of geological violence as the Pacific does from the crunching of the earth's plates. The sudden release of tension between plates is responsible for the frequent and deadly earthquakes in the Pacific and other regions. However, tsunamis can strike the Atlantic Coast as a result of distant earthquakes, as proven by the quake that hit near Lisbon, Portugal, on Nov. 1, 1755. Waves from that quake caused damage from England to Cuba, according to historical accounts.
Thousands of people in America might have died if the Atlantic coast had been as densely populated then as it is now, experts warn. Overall, about 53 percent of Americans live in coastal counties, and much of the world's population is concentrated along shorelines. "The same earthquake that didn't cause much damage in 1750 is going to cause huge problems in 2050," said Cliff Frohlich, associate director and senior research scientist at the University of Texas at Austin's Institute for Geophysics and co-author of the book Texas Earthquakes. "The magnitude of the disaster is so much greater now." |
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| The Dallas Morning News; Jan. 2, 2005 |
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