Wednesday, 17 March 2010

Dinosaurs WERE wiped out by an asteroid crashing into Earth - Pictures

Some believe they were killed off by massive volcanoes , others that they were a victim of prehistoric climate change.
Now a major study claims to have conclusive proof that dinosaurs were wiped out within weeks of an asteroid the size of the Isle of Wight slamming into the Earth. Researchers say the impact sent a vast flume of dust into the atmosphere 65 million years ago, unleashed a torrent of powerful earthquakes and triggered forest fires across North America, blocking out the sun and wiping out half of all species.
The panel of 41 international experts - including British researchers from Cambridge, Imperial College and the University of London - looked at 20 years of research to settle the long-running debate about what killed the dinosaurs.
The mass extinction event also wiped out the bird-like pterosaurs and the large marine reptiles - clearing the way for mammals to become the dominant species on Earth.
Scientists have long argued about whether the dinosaurs were killed by a space collision or by volcanic activity in India, where a series of 'super volcanoes' erupted for more than a million years, cooling the atmosphere and triggering torrential acid ran.
Dr Joanna Morgan, co-author of the review at Imperial College London, said: 'We now have great confidence that an asteroid was the cause of the extinction.

'This triggered large-scale fires, earthquakes measuring more than 10 on the Richter scale and continental landslides, which created tsunamis. 'However, the final nail in the coffin for the dinosaurs happened when blasted material was ejected at high velocity into the atmosphere. 'This shrouded the planet in darkness and caused a global winter, killing off many species that couldn't adapt to this hellish environment.' The paper, published in Science, pieces together powerful evidence collecting since the 1990s. The collision triggered large-scale fires, earthquakes and continental landslides
The 'smoking gun' is the 65-million-year-old layer of iridium that is found in rocks all over the world.
The metal is extremely rare in the Earth's crust, but is common in asteroids and almost certainly came from a collision with a massive asteroid. Geologists have also found large amounts of 'shocked quartz' dated to the same time. The mineral is created during meteorite collisions or nuclear explosions.
The fossil record shows that immediately after the asteroid impact, there was a dramatic fall in the number of animals species. In the previous 500,000 years, however, there are no signs of species dying out - despite the large number of active 'super volcanoes'. Scientists say that is more proof that an asteroid - and not volcanoes - killed off the dinosaurs.

Power: The impact of the asteroid unleashed a torrent of powerful earthquakes and triggered forest fires, wiping out half of all species. Researchers have also found a 65-million-year-old 125-mile-wide crater - caused by the impact with a nine-mile-wide asteroid - at Chicxulub, Mexico. The asteroid is thought to have hit the Earth with the force of one billion Hiroshima-sized atomic bombs - and would have blasted material at high speed into the atmosphere where it would have blocked out the sun. Computer models also suggest that the gases spewed out by the Indian volcanoes would have been short-lived - and unable to trigger a mass extinction, the researchers say. Dr Gareth Collins, of Imperial College London, said: 'The asteroid was about the size of the Isle of Wight and hit Earth 20 times faster than a speeding bullet.
'The explosion of hot rock and gas would have looked like a huge ball of fire on the horizon, grilling any living creature in the immediate vicinity that couldn't find shelter.
'Ironically, while this hellish day signalled the end of the 160-million-year reign of the dinosaurs, it turned out to be a great day for mammals, who had lived in the shadow of the dinosaurs prior to this event.
'The extinction was a pivotal moment in Earth's history, which ultimately paved the way for humans to become the dominant species on Earth.'

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