Scientists reaffirm theory that giant asteroid killed dinosaurs
The researchers analyzed evidence and agreed it supports a single-impact theory first proposed 30 years ago on the cause of the mass extinction.
Since 1980, scientists have gathered an overwhelming amount of evidence that shows a single asteroid about 6 miles in diameter and traveling at thousands of miles an hour, slammed into the Gulf of Mexico, said Richard Norris, a paleoceanographer at the University of California San Diego.
The impact caused a crater 24 miles deep and 125 miles wide, according to Norris, who was part of the research team.
The crater was discovered in 1991 in Chicxulub, Mexico, on the Yucatan Peninsula, said scientists who called it the "smoking gun" that backed up the asteroid theory.
Norris compared the asteroid's impact with a blast from 100 million tons of TNT.
"It's basically more powerful than all the atomic weapons on the planet going off all at once," he said.
The researchers wanted to settle disputes about what killed off the dinosaurs. Some theories have argued that it would have taken many meteorites to cause such a cataclysmic event. Another rival theory suggested that the mass extinction was a result of a massive volcanic eruption in India that took place around the same time as the impact.
However, evidence now shows that one monster impact caused the ecological catastrophe, Norris said.
Data at the crater's location showed rock with concentrations of iridium and platinum, which are characteristic of the chemical fingerprints of the asteroid, Norris said.
Norris speculates it took about 15 million years before the planet and surviving species started recovering from the impact that also destroyed 70 percent of other species.
"It's believed that the impact actually blew down the forests over most of North America from the pressure wave associated with the explosion," Norris said.
"Then there was this fireball that came after that that fried a lot of vegetation and basically cleaned off the landscape over most of North America."
Scientists say the impact also caused a huge earthquake.
It "jiggled loose a lot of sediment on the eastern seaboard," Norris said.
The conclusion was published in the journal Science on Friday.
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Donald Wolberg - 3/10/2010
One suspects that when a group of people, scientists, politicians, poets, or taxicab drivers, feel the need to gather and tell the world wht the "current acceptable notion" of whatever happens to be, they must be responding to contrary views and feel threatened, or trying to plug holes in the theoretical dike that may have leaks. And so it is with climate change and sloppy science and dumb politics. And so it may be with the asteroid mantra, especially in the face of devastating scientific resouslt of no less an authority then Dr. Gerta Keller of Princeton and her co-workers. In a series of papers, Dr. Keller has shown clearly that the extinction scenarios of asteroids and nuclear-equivalent blasts has been overacted and less than viable. Dr, Keller's work does not stand alone, of course. Dr. Robert Sullivan long ago looked at the occurrences of dinosaur fossils and pointed out that many lineages were extinct millions of years before the supposed boundary disaster. Other scientists have documented the extinction of many marine invertebrates in Western North America, but this is clearly associated with the withdrawal of the seaway that occupied Western North America. Geologists and paleontologists have acquired a great deal of data related to the massive outpourings of volcanic material of the Deccan traps in Asia that straddle the boundary between the age of dinosaurs and mammals, the Cretaceous/Tertiary boundary at 65 million years or so. Of course many more animals and plants sem to have managed to come across the supposed "death zone" of the asteroid laden neocatastrophists, and if birds are dinosaurs, then dinosaurs dot not go extinct. We can find them on our holiday tables as turkeys, or the first robins of Spring.
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