mass extinction

mass extinction

Asteroid, Volcanoes Double Whammy Doomed Dinosaurs

6d ago
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Dinosaurs were wiped out by a double-whammy disaster caused by a meteor impact followed by a volcanic storm, compelling new evidence has shown. The creatures' 160 million-year reign is said to have ended when a six-mile wide asteroid or comet smashed into the Earth off the coast of Mexico 66 million years ago, changing the climate around the world. But some experts insist that the impact was a red herring and the real reason for the mass extinction was a surge of volcanic activity in a region of India known as the Deccan Traps. Now a new study looks set to end the debate by linking the two events. Scientists believe the meteor collision shook up the Earth so much that it turned up the volcanic heat. Within 50,000 years of the impact, the Deccan Traps volcanoes doubled their output, blanketing the Earth with sulphurous gas and dust. Together, the impact and volcanism caused a dramatic change in climate as the sun's rays were blanketed out in a version of the 'nuclear winter' predicted to follow a global nuclear war. The evidence is based on new measurements dating layers of volcanic rock to track the progress of the Deccan Traps that were more accurate than any made before. Lead scientist Professor Paul Renne, from the University of California at Berkeley (UC Berkeley), US, said: 'Based on our dating of the lavas, we can be pretty certain that the volcanism and the impact occurred within 50,000 years of the extinction, so it becomes somewhat artificial to distinguish between them as killing mechanisms: both phenomena were clearly at work at the same time.' The research, published in the journal Science, suggests that the impact abruptly changed the volcanoes' 'plumbing system' so that eruptions became less frequent but much more powerful. The average rate at which fiery magma was hurled out of the Earth roughly doubled, the study showed. These enhanced eruptions continued long after the dinosaurs died out, delaying the recovery of life for some 500,000 years after the 'KT boundary' - the point in time marking the end of the Cretaceous and start of the Tertiary period. 'We are proposing that the volcanism unleashed and accelerated right at the KT boundary suppressed the recovery until the volcanoes waned,' Prof Renne said. Co-author Professor Mark Richards, also from UC Berkeley, said: 'If our high-precision dates continue to pin these three events - the impact, the extinction and the major pulse of volcanism - closer and closer together, people are going to have to accept the likelihood of a connection among them. 'The scenario we are suggesting - that the impact triggered the volcanism - does in fact reconcile what had previously appeared to be an unimaginable coincidence.' He pointed out that a large nearby earthquake similar in size to the one that struck Japan in 2011 could also have re-ignited the Deccan Trap volcanoes. In fact it was possible that large earthquakes had triggered volcanic eruptions throughout the Earth's history. But in this case it appeared much more likely that a meteor impact rather than an earthquake set off the volcanic surge. The impact site is believed to be the 125 mile (200km) wide Chicxulub crater buried underneath the Yucatán Peninsula in Mexico. When the six-mile-wide (10km) asteroid hit what is now Mexico approximately 66 million years ago, dinosaurs were experiencing environmental upheaval, which left them vulnerable. Previous researcher has questioned the theory that a global firestorm accompanied the asteroid that killed off the dinosaurs. A team of researchers has found that heat near the impact site would not have been sufficient to ignite plants.