The Sixth Extinction: An Unnatural History

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The Chicxulub crater, off the Yucatán Peninsula, is buried under half a mile of sediment.
“Those eleven years seemed long at the time, but looking back they
seem very brief,” Walter told me. “Just think about it for a moment. Here
you have a challenge to a uniformitarian viewpoint that basically every
geologist and paleontologist had been trained in, as had their professors
and their professors’ professors, all the way back to Lyell. And what you
saw was people looking at the evidence. And they gradually did come to
change their minds.”




WHEN the Alvarezes published their hypothesis, they knew of only
three sites where the iridium layer was exposed: the two Walter had
visited in Europe and a third, which they’d been sent samples from, in
New Zealand. In the decades since, dozens more have been located,
including one near a nude beach in Biarritz, another in the Tunisian
desert, and a third in suburban New Jersey. Neil Landman, a
paleontologist who specializes in ammonites, often takes field trips to this
last site, and one warm fall day I invited myself to tag along. We met in
front of the American Museum of Natural History, in Manhattan, where

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