| Scientists confirm officially: dinosaurs wiped out by a giant asteroid strike on Earth |
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05/03/2010 17:35 (709 Day 01:58 minutes ago) | |||||
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The FINANCIAL -- A major international study has found that a massive asteroid impact on Earth wiped out dinosaurs 65.5 million years ago.
A new report from 41 international experts discounts an alternative theory that volcanic eruptions ended the reptiles' 160 million-year reign, Press Association reports. The scientists reviewed 20 years' worth of evidence in search of a definitive answer to the mystery of what happened to life on Earth around 65 million years ago.
According to the same source, more than half of all species on the planet, including the dinosaurs, flying pterosaurs, and large marine reptiles, vanished in the Cretaceous-Tertiary (KT) mass-extinction.
The study, conducted by scientists from Europe, the United States, Mexico, Canada and Japan and published in the journal Science, found that a 15-kilometre (9 miles) wide asteroid slamming into Earth at Chicxulub in what is now Mexico was the culprit, Reuters reports. "We now have great confidence that an asteroid was the cause of the KT extinction. This triggered large-scale fires, earthquakes measuring more than 10 on the Richter scale, and continental landslides, which created tsunamis," said Joanna Morgan of Imperial College London, a co-author of the review.
The asteroid is thought to have hit Earth with a force a billion times more powerful than the atomic bomb at Hiroshima, according to the same source. Morgan said the "final nail in the coffin for the dinosaurs" came when blasted material flew into the atmosphere, shrouding the planet in darkness, causing a global winter and "killing off many species that couldn't adapt to this hellish environment."
The evidence for the impact comes in the form of iridium, found in a clay layer all around the world that dates from the time of impact. While it's extremely rare in the earth's crust, it's common in asteroids, TG Daily reports. "This clay layer - with evidence for it being impact in origin - is found at every well-preserved K-Pg boundary site in the world, showing a truly global event," says University of Texas geophysicist Sean Gulick.
In some sites close to the impact, there are two layers, and some of the recent controversy stems from this. But the team points out that at more distant sites there's only a single layer, according to the same source. And the Deccan Traps hypothesis doesn't stand up either, say the scientists. Because deep ocean temperatures were largely unaffected, the the climate recovered relatively rapidly, they say. If volcanic activity were to blame, the changes would have been far slower.
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