Throughout the 1980s, geologists compiled more evidence that supported the impact hypothesis, but Alvarez still had not found an impact site. Still believing it was in the ocean, he looked for signs of a massive deep ocean tsunami from this time period. Initial studies showed that sites in Haiti and Texas contained sediments that pointed to a possible tsunami. In the late 1980s, geologist Jody Bourgeois showed that the Brazos River site in Texas had been the site of a tsunami right at the KT boundary.

While Alvarez researched the Deccan volcanoes and the crater in Manson, Iowa, Canadian geologist Alan Hildebrand began exploring the Brazos River in Texas, and the gulf of Mexico and Caribbean sites. Hildebrand was specifically looking for tsunami evidence and any signs of a crater. Inspired by Hildebrand’s interest in this region, Alvarez considered a new way to look for tsunami damage in the rock record by examining rock layers for a gap, or “unconformity,” that tsunami erosion would have caused. As Hildebrand’s research continued, Alvarez took it more seriously. In 1991, collaborating with other geologists, Hildebrand revealed in a published paper that the Chicxulub crater on Mexico’s Yucatan peninsula was the result of a late Cretaceous asteroid impact.