Disaster-movie-type predictions that a potential undersea disturbance could unleash a giant tsunami, or tidal wave, on the United States' low-lying Eastern Seaboard are probably overblown. Sparked by a report in this month's issue of the journal Geology that researchers have discovered cracks in the continental shelf off Virginia, residents have been alarmed by visions of 20-foot waves heading toward North Carolina, Virginia and Washington, D.C. The scientists behind the report, however, are very cautious in saying that such an event is highly unlikely. "This is a possible disaster kind of scenario, but it's just a possibility at the present time," said Jeffrey Weissel of Columbia University, one of the researchers who discovered the cracks.
Tsunamis — very rare in the Atlantic, but a regular threat to Pacific shores — are caused by submarine earthquakes, landslides and volcanic activity. Part of the reason for the scientists' caution over the Virginia discovery is that they don't know if the cracks are longtime formations that have gone unnoticed or a more recent phenomenon. They do know, however, that they form part of a wide scar caused by a landslide that occurred 16,000 to 18,000 years ago. Such a slide could be triggered by undersea seismic activity or the decomposition of gas hydrate deposits, a very rare occurrence on the East Coast continental shelf but one that would have devastating consequences. We'll know more about the situation this summer when the researchers go back to try and determine whether the cracks are new.