2013-02-07. New evidence comet or asteroid impact was last straw for dinosaurs

posted Feb 16, 2013, 6:39 AM by Alan Gould

| Robert Sanders, UC Berkeley News Center. Relevant to GSS Life and Climate chapter 9. Excerpt: The demise of the dinosaurs is the world’s ultimate whodunit. Was it a comet or asteroid impact? Volcanic eruptions? Climate change? ...In an attempt to resolve the issue, scientists at the Berkeley Geochronology Center (BGC), the University of California, Berkeley, and universities in the Netherlands and the United Kingdom have now determined the most precise dates yet for the dinosaur extinction 66 million years ago and for the well-known impact that occurred around the same time. The dates are so close, the researchers say, that they now believe the comet or asteroid, if not wholly responsible for the global extinction, at least dealt the dinosaurs their death blow. “The impact was clearly the final straw that pushed Earth past the tipping point,” said Paul Renne, BGC director and UC Berkeley professor in residence of earth and planetary science. “We have shown that these events are synchronous to within a gnat’s eyebrow, and therefore the impact clearly played a major role in extinctions, but it probably wasn’t just the impact.” The revised dates clear up lingering confusion over whether the impact actually occurred before or after the extinction, which was characterized by the almost overnight disappearance from the fossil record of land-based dinosaurs and many ocean creatures. The new date for the impact – 66,038,000 years ago – is the same within error limits as the date of the extinction, said Renne, making the events simultaneous. He and his colleagues will report their findings in the Feb. 8 issue of the journal Science…. Read the full article: http://newscenter.berkeley.edu/2013/02/07/new-evidence-comet-or-asteroid-impact-was-last-straw-for-dinosaurs/