While it is generally believed that a massive meteor crash was responsible for the extinction of dinosaurs on the Earth, many paleontologists say that the cause may have been more complex than previously believed.
Princeton University paleontologist Gerta Keller believes that a single meteor did not have the capacity to kill off all dinosaurs. Multiple meteorite impacts, massive volcanic activity coupled with irreversible climate change were the main causes for the extinction of dinosaurs, Keller told at the annual meeting of the Geological Society of America in Philadelphia.
The Chicxulub meteorite impact is thought to have wiped out the dinosaurs altogether, but Keller believes that this impact, though powerful, was not enough. "The Chicxulub impact alone could not have caused the mass extinction because this impact predates the mass extinction," said Keller.
Science has accepted that the so-called K-T extinction event, which occurred 65 million years ago, accounted for all non-avian dinosaurs. But Keller and colleagues argue that the Chicxulub impact, which left a 100-mile crater in Mexico occurred 300,000 years before dinosaurs became extinct.
The Chicxulub impact along with a massive surge in volcanic activity "dealt the final blow to a Cretaceous biota already on the brink of extinction," Keller said, adding that the stress generated by the event had the potential to reduce the size of population on the Earth.
Applying their model to the current period, the researchers warned that the planet was getting stressed again, "Under [current] conditions any disaster that might strike (impact or volcanism or major greenhouse warming), which ordinarily would not cause major extinctions, will put much of Earth's biota at risk of extinction," Keller said.
They examined geologic data from the last 488 million years and concluded that species got extinct when the environment was stressed to saturation point and burst open as a result. "Periods of stress are going to reduce population sizes," said Nan Arens of Hobart and William Smith College in New York.
The researchers summarized the events leading up to the extinction of the dinos by saying that the volcanic eruptions triggered massive climate change. This was followed by the meteorite impact, which was simply unbearable.
