How do scientists know that a meteorite killed the dinosaurs?
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So fossils (and other things) are found in layers according to how old they are. The older fossils are found deeper in the Earth. There’s a boundary above which no non-avian dinosaur fossils are found, at about 66 million years ago. This is called the K-Pg boundary, where the Cretaceous period ends and the Paleogene period begins.
At this boundary, they found way high concentrations of iridium, as high as 160 times normal. Iridium is rare in and above the crust–when the planet formed, it mostly sank into the core, being that it’s so heavy. But a meteor could have a lot of it. That was the first major proof of the impact event. Other evidence was also found, like shocked quartz, something that’s found at the site of meteor impacts and nuclear explosions.
Then the Chixulub crater was discovered, and this was tied to the evidence that had been found.
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