Scientists hypothesized that the Mass Extinction at the K-Pg boundary was due to an asteroid impact by looking at the rock record without actually finding an impact crater.

Question

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Scientists noticed a thin layer of clay-rich sediment in the rock record around the K-Pg boundary, which contained high levels of iridium, a rare element found in meteorites. This led them to hypothesize that an asteroid impact caused the mass extinction, even though they had not yet found a impact crater. The Chicxulub crater in Mexico was later discovered and confirmed as the impact site.

Scientists Hypothesized That the Mass Extinction at the K-Pg Boundary