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The idea that ocean impacts from asteroids as small as 100 meters in diameter can create gigantic destructive waves, known as tsunamis was first proposed in 1993 at a Asteroid Hazard meeting in Arizona. It was suggested that throughout history every 250 years an impact caused a hazardous wave that destroyed coastal settlements. At the time the ideas were thrown in to controversy by the late astrophysicist J. Mayo Greenberg. He stated that the people living in the below sea level Netherlands had not for the past 1 000 years experienced a tsunami every 250 years like the theory predicted.
Following investigations by planetary scientist Jay Melosh of Lunar and Planetary Laboratories, Arizona University, revealed new evidence in support of Greenberg. Melosh checked with Dutch geologists who had drilled the basement rock in the Rhine river delta. The core sample showed the past 10 000 years, with only one large tsunami 7 000 years ago. Although this event coincided almost exactly with a giant landslide off the coast of Norway, and not the result of an ocean-asteroid impact.
Melosh’s research also showed that predictions for the size of these catastrophic waves were greatly exaggerated. Using a U.S Naval report from 1968 that was previously unauthorised, he concluded that waves produced by small bombs or meteorite impacts were smaller than tsunami waves. Explosive waves or small impact generated waves will break up on the outer continental shelf and produce little onshore damage, a phenomena know within the defence community as the “Van Dorn effect”. Named after the author of the 1968 report.
More info: Science magazine
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