raphic Institution in Massachusetts, who helped to discover the Black Ridge feature, agrees that lots of methane could have been released from that site, had it been trapped in the form of methane hydrate. He adds that the increased preponderance of the isotope carbon-12 over carbon-13 immediately after the impact also suggests that lots of methane was burnt. But he says this isotopic pattern is not repeated all over the globe.

Other experts are similarly cautious. "I think this idea is very intriguing," says Peter Schultz of Brown University in Providence, Rhode Island, who has studied the late Cretaceous impact. "But I'm not sure even an impact this big would have liberated that amount of methane."

Nevertheless, even local firestorms could have contributed to the dinosaurs' demise. Angela Milner, head of vertebrate palaeontology at the Natural History Museum in London, says that many dinosaurs appear to have been in serious decline before the impact. But she agrees that huge methane fires "could have been the final straw" for some species.

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Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-20-7331-2751
New Scientist
16-Nov-1999

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