T. Rex and the Crater of Doom the Brazos river that a tsunami has swept across the Gulf of Mexico millions of years earlier. The discovery was made thanks to a graduate student named Alan Hildebrand that notified Alvarez of the evidence of a crater on the Yucatan peninsula, which had never been published in the scientific literature by the Mexican petroleum geologists that had found it. The age of the crater needed to be determined if it was going to be a candidate for the KT boundary impact, but access to the region was limited by the crater being buried over time and the core samples
Chicxulub crater is the larger Shiva crater, though the structure's status as an impact crater is contested. The collision of Comet Shoemaker–Levy 9 with Jupiter in 1994 demonstrated that gravitational interactions can fragment a comet, giving rise to many impacts over a period of a few days if the comet should collide with a planet. Comets undergo gravitational interactions with the gas giants, and similar disruptions and collisions are very likely to have occurred in the past. This scenario may have occurred on Earth at the end of the Cretaceous, though Shiva and the Chicxulub craters might have been formed 300,000 years