Experts say the risks are greater than most people realize.
DALLAS MORNING NEWS
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.
A look at history
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.