Dinosaurs: Hard to Kill

It took a lot more than just one meteor slamming into Mexico to wipe out the big lizards, it turns out:

There’s growing evidence that the dinosaurs and most their contemporaries were not wiped out by the famed Chicxulub meteor impact, according to a paleontologist who says multiple meteor impacts, massive volcanism in India, and climate changes culminated in the end of the Cretaceous Period.

The Chicxulub impact may, in fact, have been the lesser and earlier of a series of meteors and volcanic eruptions that pounded life on Earth for more than 500,000 years, say Princeton University paleontologist Gerta Keller and her collaborators Thierry Adatte from the University of Neuchatel, Switzerland, and Zsolt Berner and Doris Stueben from Karlsruhe University in Germany. A final, much larger and still unidentified impact 65.5 million years ago appears to have been the last straw, exterminating two thirds of all species in one of the largest mass extinction events in the history of life. It’s that impact — not Chicxulub — which left the famous extraterrestrial iridium layer found in rocks worldwide that marks the impact that finally ended the Age of Reptiles.

“The Chicxulub impact could not have caused the mass extinction,” says Princeton University paleontologist Gerta Keller, “because this impact predates the mass extinction and apparently didn’t cause any extinctions.”

deccan-flood-basalts.jpgThe climate changes, caused in part by greenhouse gases released from “prolonged and massive eruptions” of the Deccan Flood Basalts in India, were pretty extreme: Oceans 3 or 4 degrees warmer, and land temperatures 7 or 8 degrees warmer, 20,000 years before, and 100,000 years after, the Chicxulub meteor struck. Marine life was affected by growing smaller and reproducing more offspring — to increase the odds for survival. Tropical species were on the edge of extinction. Then there was another huge meteor impact, comparable to the first. Where did that meteor strike? Scientists don’t know, although some are suggesting a 500-kilometer-wide crater in India might be a remnant of it.

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