The iridium layer
A father and son proposed that an asteroid killed the dinosaurs
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The resistance was strong and reasoned: geology had spent a century ridding itself of catastrophe explanations, and an asteroid looked like a relapse. Confirmation came when the Chicxulub crater in the Yucatán was identified in 1991 — it had been known to oil companies since the 1970s, but nobody had made the connection. The hypothesis now stands as the leading explanation, with Deccan volcanism a contributing factor still argued over.
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Walter Alvarez, a geologist, showed his father — the physicist Luis Alvarez — a thin clay layer lying exactly where the dinosaurs disappear. They measured it and found iridium, an element rare on Earth and common in asteroids. Their proposal was rejected for eleven years, until the crater was found.
Sources
- Alvarez, Alvarez, Asaro & Michel, Science 208 (1980)
- Schulte m.fl., Science 327 (2010) — samlet vurdering av Chicxulub
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