What killed the dinosaurs?
Debate continues over cause of extinction
It took more than a meteorite to wipe out dinosaurs 65 million years ago, according to a paleontologist who suggests that multiple meteorite impacts, massive volcanic activity and climate change caused the extinction of dinosaurs.
This contradicts the mainstream belief that a giant meteorite smashed into the Yucatan peninsula in Mexico, causing environmental chaos and the extinction of dinosaurs.
Growing evidence shows that the dinosaurs were not wiped out by the famed Chicxulub meteorite impact alone, said Princeton University paleontologist Gerta Keller, who presented her findings at the annual meeting of the Geological Society of America in Philadelphia this week.
"The Chicxulub impact alone could not have caused the mass extinction because this impact predates the mass extinction," said Keller.
A final, much larger and still unidentified impact 65 million years ago appears to have been the deciding element,killing two-thirds of all species, according to Keller.
Marine sediments drilled from the Chicxulub crater, as well as from a site in Texas along the Brazos River and from outcrops in northeastern Mexico, reveal that the Chicxulub meteoritehit the earth 300,000 years before the mass extinction.
Microscopic marine animals were left virtually unscathed, according to Keller and her team of scientists.
The Chicxulub impact, though violent,worked with volcanic eruptions and climate change to push dinosaur species toward the brink of extinction.
The dinosaursdisappearedafter this second and larger meteorite impact, said Keller. But her team couldn't say what happened to the crater from that second impact.