Landslide or asteroid?
The origin of such a tsunami is also under debate. An undersea landslide is the most likely source, but one research group has proposed that an asteroid impact provided the trigger.
In 300BC, barrier beaches and marsh grass embroidered the coast, and Native Americans walked the shore.
Today, a wave of the proposed size would leave Wall Street and the Long Island Expressway awash with salt water.
Atlantic tsunamis are rare,
but could be triggered
by submarine landslides
An Atlantic tsunami was rare but not inconceivable, said Neal Driscoll, a geologist from Scripps Institution of Oceanography, who is not associated with the research. But verifying one that is 2,000 years old is tricky.
Earthquakes, underwater landslides, or a combination of the two were the most frequent Atlantic tsunami triggers, said Professor Driscoll.
The 1929 Grand Banks tsunami, in Newfoundland, which killed more than two-dozen people and snapped many transatlantic cables, was set in motion by a submarine landslide set off by an earthquake.
Dr Goodbred imagines that the New York wave was on the Grand Banks scale - three to four meters high and big enough to leap over the barrier islands; but that it did not reach the magnitude of the 2004 Sumatran tsunami.
The evidence is buried under metres of sediment in New York and New Jersey.
