Researchers say they have found marks left behind as tsunamis produced by the infamous dinosaur-killing asteroid reached shallow waters off North America 66 million years ago. If they're right, these are the largest such formations on Earth. Dr Gary Kinsland of the University of Louisiana at Lafayette was involved in two seemingly unrelated projects when an unexpected connection was revealed. He was studying the Chixculub crater that marked the end of the Cretaceous Era. Meanwhile, he was also assigning graduate students to map the presence of coalbed methane in northern Louisiana using ground-penetrating radar that reflects off changes in subsurface composition.