Megaripples are large ripple-like features that have wavelengths greater than one meter or a ripple height greater than ten centimeters. These geological sand waves are also called subaqueous dunes. The largest known megaripples were found hidden deep under Louisiana, and experts believe that they were formed after the asteroid crash that killed the non-avian dinosaurs, as Space details:
The 52-foot-tall (16 meters) megaripples are about 5,000 feet (1,500 m) under the Iatt Lake area, in north central Louisiana, and date to the end of the Cretaceous period 66 million years ago, when that part of the state was underwater, the researchers said. The megaripples' size and orientation suggest that they formed after the giant space rock, known as the Chicxulub asteroid, slammed into the Yucatán Peninsula, leading to the Chicxulub impact tsunami, whose waves then rushed into shallower waters and created the megaripple marks on the seafloor, the researchers said.
The occurrence of "ripples of that size means something very big had to disturb the water column," study lead researcher Gary Kinsland, a professor in the School of Geosciences at the University of Louisiana at Lafayette, told Live Science. "This is just further evidence that the Chicxulub impact ended the Cretaceous period."
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