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New Mexico State University

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NMSU research further links dinosaur extinction with meteor collision, tsunami

Recently published research by a New Mexico State University professor is likely to rekindle the debate over what killed the dinosaur - or more specifically, what killed the Tyrannosaurus rex.

Timothy Lawton, head of geological sciences at NMSU, said his paper published in this month's Geology supports the idea that a massive extinction followed the crash of a giant meteor or comet into the Earth's surface 65 million years ago.

The collision dug the Chicxulub crater 40 kilometers deep off the coast of what is now the Yucatan Peninsula. The impact was greater than 10,000 times the entire nuclear arsenal of the world, according to scientist Walter Alvarez in his book "T. rex and the Crater of Doom." The shock waves sent debris hurtling over thousands of miles, eventually creating a kind of nuclear winter, Lawton said.

The impact also spawned a massive tsunami that spread over the Gulf of Mexico, carving deep slashes in the ocean floor and sending waves of destruction across the coastland. The waves could have traveled as far as 180 miles inland, Lawton said, noting that the devastating tsunami in the Indian Ocean on Dec. 26 was small compared to the one that followed the Yucatan collision.

All of this spelled doom for the dinosaurs who could not survive the disaster, according to the theory Lawton's paper supports, and accounts for their disappearance at the end of the Cretaceous period in Earth's history.

These waves also carried bits of debris from the collision and spread them back and forth across the region. Evidence of this activity has been found as far north as Waco, Texas - and is often manifested by the appearance of what seems to be bits of glass created by the cooling of molten detritus.

The tsunami mixed the debris and sloshed it around, settling some and carrying sediment and fossils from the coast back into the ocean's depths, Lawton said. Proof of this backrush lies in deposits found scored into the continental shelf. They provide evidence of a massive sediment recycling system at the end of the Cretaceous period.

Other scientists dispute the theory because those fossils on the top of the crater predate the dinosaur extinction by hundreds of thousands of years and don't appear to have been laid down by great chaos.

Lawton contends the sloshing and recycling are the very reason those fossils are found on top of the crater. And he adds that as the backwash from the tsunami slowed it became somewhat languorous and that final languid movement - not activity over the ages - accounts for the seemingly careful layering of fossils and rocks in the region.