Astronomers and marine geologists are abuzz, the New York Times reports, over the "Holocene Impact Working Group" and their theory that megacatastrophic meteor hits on our big blue marble are more common than commonly believed–and that one may have smacked the Indian Ocean as recently as 4,800 years ago.
The key to their story is "chevrons"–inland sediment deposits–that the Working Group apocalypticians think can be explained only by huge huge waves. No, even bigger than you are imagining. "No tsunami in the modern world could have made these features," says Ted Bryant, a geomorphologist at the University of Wollongong in New South Wales, Australia, who thinks they are caused by meteor hits. "End-of-the-world movies do not capture the size of these waves. Submarine landslides can cause major tsunamis, but they are localized. These are deposited along whole coastlines."
Burckle crater, recently discovered 900 miles southeast of Madagascar, site of some intriguing "chevrons," was found by looking for it based on the theory that inland chevrons=meteor impacts somewhere relatively nearby in the ocean. Dallas Abbott, an adjunct research scientist at Lamont-Doherty Earth Observatory in Palisades, N.Y. who searches for, and often finds, big holes in the ocean based on chevrons on land, believes the crater is only 4,500-5,000 years old, though it has not been authoritatively dated. Abbott has interpreted chevrons 4 miles inland in Australia as being connected to ocean craters whose sediment cores "contain melted rocks and magnetic spheres with fractures and textures characteristic of a cosmic impact." And that impact might be only 1,200 years old.
This conclusion about big object hits being this frequent and recent goes against dominant astronomical beliefs, so there are understandably many doubters. One of the doubts as expressed in the NY Times doesn't make instant sense to me. Dr. David Morrison of the NASA Ames Research Center says that: "We know what's out there, when they return, how close they come…there is no reason to think we have had major hits in the last 10,000 years."
But if what the Holocene Impact people are saying is true, then the specific objects that slammed Earth are no longer out there, no longer returning, and already came as close as they're ever gonna get. Perhaps establishment astronomers out there can further explain how our recent telescopic observations of what's floating around our solar system can unequivocally tell us that it isn't possible that a big rock hit us as recently as 4,500 years ago? Is it based on a belief that all these objects come in groups, and that the rest of the groups' orbits and approaches are well understood? Otherwise, not sure what to make of Dr. Morrison's comment.