One well-placed asteroid could flood East Coast Astrophysicist says Baltimore and D.C. would be under water

January 08, 1998|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

WASHINGTON -- Just when you've got the house and yard the way you want them, along comes this astrophysicist from New Mexico who says an asteroid splashing down in the mid-Atlantic would wash it all away.

The tidal wave triggered by such an impact "would probably wipe out Baltimore," said Jack Hills, of the U.S. Department of Energy's Los Alamos National Laboratory.

If the rock from space were big enough -- say, 3 miles wide -- the 300-foot wave, or tsunami, would also surge over Long Island, southern New Jersey, the entire Delmarva peninsula, southern coastal regions as far inland as the Appalachian foothills and all their coastal cities.

Across the Atlantic, west-facing coastal regions of Spain, Portugal, France, Britain and Ireland would also be raked by the advance and retreat of the roiling, debris-choked wave.

If the asteroid fell in the Pacific between Hawaii and California, Honolulu and the Los Angeles basin would be swamped, said Hills.

He presented his computer-generated forecasts yesterday to scientists in Washington attending the 191st meeting of the American Astronomical Society.

With no more than a few hours' warning after such an impact, death tolls would be in the millions, and property damage would far exceed any prior natural catastrophe.

"This scares me," said Hills. Although he's safe in New Mexico, he said, his mother-in-law lives in coastal Maine.

No one was seen running from the meeting in panic.

Hills, 54, said the chances of such a calamity's actually occurring are tiny.

Asteroids 3 to 4 miles across strike Earth only once in 10 million years on average.

On the other hand, he said, a space rock as small as 200 meters (656 feet) in diameter -- a bit more than the length of two football fields -- can be expected once in 3,000 to 5,000 years.

That's big enough to trigger a tsunami, and the wave would cause "devastating damage, much larger than has been seen for any earthquake tsunami seen [until] now," Hills said.

And the damage would be far more widespread.

A 200-meter rock crashing into the mid-Atlantic at 12 miles per second would generate a circular wave perhaps 10 feet high and send it rippling across the deep ocean at the speed of a jetliner, Hills said.

That would give East Coast residents perhaps three hours' warning, assuming anyone noticed the impact.

Some Defense Department satellites might spot it, but there are no mechanisms yet for translating such data into public warnings, Hills said.

As it approached the coast, the tsunami would slow down and increase in height to perhaps 100 feet -- as high as a 10-story building.

In New York, he said, the water probably would not arrive as a monstrous, breaking wave. It would rise gradually to that height over 20 or 30 minutes. But it would be too fast to outrun.

After reaching high water -- an average of 6 miles inland on the East Coast -- the wave would begin to retreat, laden now with rocks and building debris that would scour the land it had flooded.

"It's a mean-looking thing," Hills said.

Over the next seven hours, according to Hills' calculations, the ocean water would continue to oscillate, sending repeated, though diminishing, waves rolling across a devastated landscape.

Geologists have found evidence of catastrophic tsunamis in several places around the world.

For example, there are deposits of loose coral 1,000 feet above sea level on the island of Lanai in Hawaii, believed to have been dumped there by a tsunami 90,000 years ago.

But all known tsunami debris is believed to have been caused by earthquakes rather than asteroid impacts in the ocean.

The historical record holds no reports of tidal waves linked to "falling stars," Hills said.

But for most of history, "there are only a few 'footprints' [regions] on Earth where people were writing records."

Maybe there was no one around to record such an event.

Hills' team at Los Alamos will spend an additional three years refining their computer studies to provide more finely detailed maps of coastal regions vulnerable to asteroid-induced tsunamis.

Although Hills would favor it, the United States has no plans for now to use nuclear weapons labs such as Los Alamos to develop systems for deflecting or destroying any asteroids that threatened the planet.

Pub Date: 1/08/98

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