Layers of meaning
Knowledge trapped in stone
THE dinosaurs, as every schoolchild knows, died out 66m years ago, at the end of the Cretaceous period. But there is an argument about whether they went with a bang or a whimper. The bang brigade blame an asteroid that hit Earth at exactly the right time (the crater it created is in southern Mexico). This would have caused fires around the planet and thrown up a dust cloud that may have obscured the sun for decades. The whimperers blame a longer period of ecological stress—the result of huge volcanic eruptions in what is now India poisoning the atmosphere.
Some people think both were needed to push life over the edge (it was not only dinosaurs; a large fraction of other animal species succumbed, too). But one possibility has never been nailed down. This is that the impact actually caused the eruptions. That is the thesis of Paul Renne of the University of California, Berkeley, and his colleagues. And in this week’s Science they publish a plethora of data on rocks from the period to back that thesis up. Read more.