A group of scientists analyzing sedimentary deposits from more than 20 core samples taken around New York are increasingly confident that a rare Atlantic Ocean tsunami slammed the Northeast coastal region in 300 BC. The cause? An asteroid, theorizes one group led by geologist Dallas Abbot. Usually tsunamis are triggered by oceanic landslides, but her team discovered meteoritic material such as carbon spherules and nanodiamonds in the New Jersey and Hudson River cores dating to 2,300 ago. Scientists are planning to perform more radiocarbon tests on other samples, but that's just a formality: If it happened once, it will happen again, so check the sump pump in the basement—if you've got a basement! Researcher Steven Goodbred tells the BBC, "If we're wrong, it was one heck of a storm." Were it to hit New York today, scientists say a tsunami of this magnitude would leave Wall Street and the Long Island Expressway in ruins. The downside is that it would also snarl the morning commute.