EXTINCTIONS × EARTH

The Asteroid That Ended the Dinosaurs

66.0 million years ago

Phanerozoic · Cenozoic · Paleogene · Paleocene

A rock about ten kilometres across struck the shallow sea off Yucatán, in the northern spring: fish killed that same day preserve the season in their bones. The blast threw sulfate and vaporised rock into the stratosphere and set fires across continents, and the sunlight failed for years. About three quarters of all species went, including every dinosaur that was not a bird.

Why it matters

One day redirected the history of life. Modelling where dinosaurs could still have lived afterwards gives the same answer from the other side: the impact winter closes their habitat worldwide, while the Indian eruptions, by warming the climate, would have opened it. If anything the volcano softened the blow.

Dating & uncertainty

Neither the impact nor its date is in doubt: the crater, the shocked quartz and the worldwide iridium layer settle both. What is argued is how much of the killing the asteroid did on its own, since the Deccan eruptions in India were under way at the same time. Fish bones from North Dakota even preserve the season: the impact fell in the northern spring.

Sources

1. Schulte et al. (2010), Science · The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary
2. Morgan et al. (2022), Nature Reviews Earth & Environment · The Chicxulub impact and its environmental consequences
3. Chiarenza et al. (2020), PNAS · Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction
4. During et al. (2022), Nature · The Mesozoic terminated in boreal spring

Earth history as one day

23:39:0320 min 56 s before midnight

if Earth’s 4.54 billion years were compressed into a single day