What Killed The Dinosaurs - Documentary

	What Killed The Dinosaurs - Documentary Until recently most scientists thought they knew what killed off the dinosaurs. A 10km-wide meteorite had smashed into the Yucatan peninsula in Mexico, causing worldwide forest fires, tsunamis several kilometres high, and an 'impact winter' - in which dust blocked out the sun for months or years. It was thought that the dinosaurs were blasted, roasted and frozen to death, in that order. But now a small but vociferous group of scientists believes there is increasing evidence that this 'impact' theory could be wrong. That suggestion has generated one of the bitterest scientific rows of recent times. The impact theory The impact theory was beautifully simple and appealing. Much of its evidence was drawn from a thin layer of rock known as the 'KT boundary'. This layer is 65 million years old (which is around the time when the dinosaurs disappeared) and is found around the world exposed in cliffs and mines. For supporters of the impact theory, the KT boundary layers contained two crucial clues. In 1979 scientists discovered that there were high concentrations of a rare element called iridium, which they thought could only have come from an asteroid. Right underneath the iridium was a layer of 'spherules', tiny balls of rock which seemed to have been condensed from rock which had been vapourised by a massive impact. On the basis of the spherules and a range of other evidence, Dr Alan Hildebrand of the University of Calgary deduced that the impact must have happened in the <b>...</b>	From: MrBestdocumentary Views: 102 1 ratings
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