A thin band of rock holds the secret to the dinosaurs' sudden, violent end.

Nature · Published 3 October 2026 Swipe more like this →

In short: Sixty-six million years ago, a massive asteroid struck Earth, triggering a mass extinction that wiped out 75% of all species. While the Chicxulub impact is the primary suspect, scientists continue to debate whether volcanic eruptions and shifting sea levels played a supporting role in this planetary catastrophe.

The Cretaceous–Paleogene (K–Pg) boundary is a distinct geological signature found worldwide, characterized by an iridium concentration hundreds of times higher than normal. First identified in 1980 by a team including Luis and Walter Alvarez, this layer marks the abrupt end of the Mesozoic Era. The discovery provided the foundation for the Alvarez hypothesis, which posits that a massive meteorite impact caused the extinction of all non-avian dinosaurs and a majority of other species.

The impact site, the Chicxulub crater, lies buried beneath Mexico's Yucatán Peninsula. Measuring over 150 km in diameter, it was formed by an asteroid roughly 10–15 km wide. Beyond the initial blast, the collision triggered colossal tsunamis and ejected sulfur-rich material into the atmosphere, creating sulfuric acid rain that devastated global vegetation and marine life. Scientific drilling in 2016 into the crater's peak ring provided further evidence confirming these catastrophic environmental effects.

While the impact is the widely accepted catalyst, the extinction narrative is nuanced. The Deccan Traps in India, a massive volcanic province, were erupting during the same period. Some researchers suggest these eruptions contributed to climate instability through greenhouse gas emissions and aerosol release. Furthermore, significant sea-level regressions occurred during the late Cretaceous, altering habitats and reducing species-rich continental shelves. Today, many scientists consider that multiple factors—including the impact, volcanism, and environmental shifts—may have collectively driven the mass extinction event.

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