Why is this been only discovered now? This type of geological signature is pretty obvious and the apparent aging tells us that the surrounding strata have been well mapped by previous work.
Then we have the fact that 2300 years ago had a lot of chatty Greeks wandering about and it was hardly prehistoric. Here lack of evidence is clear lack evidence of a lack of significant effect on Western Europe .
More bore holes are needed both north and south in order to measure the real decline curve from the epicenter. With apparent ash involved, we may have a land based effect triggering a quake close by that then brought on a local tsunami.
The apparent impact ash could even be material caught in the debris from a completely different event and the tsunami may well be from a local land slip. Not likely, but we need tight mapping now to center the event.
66-Foot Waves Hit New York
By Charles Q. Choi, LiveScience Contributor
posted: 26 October 2010 07:33 am ET
A cosmic impact two millennia ago may have sent tsunamis deluging what is now the Big Apple, scientists suggest.
Many of the giant sea waves known as tsunamis are caused by underwater earthquakes and volcanoes — for example, the devastating 2004 Indian Ocean tsunami was triggered by a quake off the northwestern coast of Sumatra . Still, the causes of nearly 10 percent of all tsunamis nowadays remain uncertain.
Cosmic impacts have been known to cause tsunamis in the past. For instance, scientists have found evidence that the Chicxulub impact in Mexico
Now researchers have evidence suggesting that an asteroid roughly 200 yards (183 meters) wide crashed off the coast of New Jersey and sent tsunamis surging toward what is now New York City
"Our models suggest the tsunamis were up to 20 meters (66 feet) high when they entered the Hudson River," said researcher Dallas Abbott, a geologist at Columbia University's Lamont-Doherty Earth Observatory in New York.
"We have layers up to maybe 30 centimeters (11.8 inches) thick," Abbott said. "They get thinner upriver, where they're more like 6 centimeters (2.3 inches) thick."
Within these potential tsunami layers is evidence of a cosmic impact, including shocked minerals and microscopic carbon beads loaded with "nano-diamonds," which are "all things only impacts can do," Abbott said. One candidate for the crater that was produced by this impact, she said, lies in the undersea Carteret Canyon , located roughly 90 miles (150 km) off the coast of New Jersey
Other scientists have raised alternate explanations for these layers. For instance, volcanic eruptions or gigantic landslides on the other side of the Atlantic might have caused the giant waves. Or these anomalous layers of sediment that Abbott and her colleagues are investigating may not have been caused by tsunamis at all — hurricanes can generate huge pulses of water known as storm surges, whose effects on sediment could resemble those of tsunamis.
"Of course, that doesn't explain the evidence of impact that we've found," Abbott said.
For a cosmic impact, one smoking gun would be a specific form of deformed rock known as shocked quartz. The rock is generated by the intense heat and pressure of a collision with an extraterrestrial object. "But if there was an oceanic impact, the oceanic crust doesn't really have quartz to shock," Abbott said.
It there were tsunamis, it remains unclear if ancient Native Americans witnessed them.
"One possible reason why Indian tribes only moved into the area relatively recently is that the people who were once there were all wiped out," Abbott said. "If you look at the predicted wave heights, there would have been few places to hide."
Abbott and her colleagues plan to detail their most recent findings Nov. 3 in Denver, at the annual meeting of the Geological Society of America
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