The end-Cretaceous extinction

What happened

At the boundary between the Cretaceous and Paleogene periods, a large asteroid hit Chicxulub, on Mexico’s Yucatán Peninsula. The extinction that followed ended the non-bird dinosaurs and many other groups.

What the evidence shows

• A single layer of debris linked to the Chicxulub impact is found worldwide at the boundary, and its timing matches the start of the extinctions.
• Modelling suggests fine dust from the impact kept the planet dark and cold for years, sharply cutting plant growth.
• Some researchers argue that ground-dwelling mammals and birds were more likely to survive than tree-dwelling ones.

What is uncertain

• How long the darkness lasted depends on the model.
• Survival did not prove that the survivors were superior. Luck, size, diet and habitat all played a part.

Sources

• Schulte et al. 2010. The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary. Science. (opens the publisher’s site)

  What it supports: A synthesis concluding that the Chicxulub impact triggered the end-Cretaceous mass extinction, based on a worldwide ejecta layer that coincides with the extinctions.

• Senel et al. 2023. Chicxulub impact winter sustained by fine silicate dust. Nature Geoscience. (opens the publisher’s site)

  What it supports: Modelling in which fine dust from the impact darkened and cooled the planet and cut plant growth. Exact durations depend on the model.

• Janis et al. 2025. Down to earth: therian mammals became more terrestrial towards the end of the Cretaceous. Palaeontology. (opens the publisher’s site)

  What it supports: Fossil limb bones suggesting that mammals in western North America were becoming more ground-dwelling towards the end of the Cretaceous.

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