Over 800 miles from the impact site, massive ripples buried deep underground record the devastation wrought by an asteroid. The Chicxulub impact, the likely smoking gun for the extinction of the dinosaurs at the end of the Cretaceous, sent tsunamis tearing across the Gulf of Mexico. These giant waves left ripples in the undersea sediments as they passed and a new study has found what might be the largest "megaripples" on the planet.