The asteroid impact was not the only killer of the dinosaurs
In short: We often imagine a single, sudden catastrophe ending the age of reptiles. While a massive asteroid strike 66 million years ago is a leading theory, the truth is far more complex. Evidence suggests dinosaurs were already facing a decline long before the final, catastrophic blow arrived.
The mass extinction 66 million years ago, which marked the transition from the Cretaceous to the Paleogene, was a devastating event that claimed three quarters of life on Earth. This included non-avian dinosaurs, pterosaurs, ammonites, and large marine reptiles like mosasaurs and plesiosaurs. However, the popular image of a sudden, singular death for all dinosaurs is a misconception. Fossil records, particularly from North America, indicate that many dinosaur groups were already in decline during the late Cretaceous.
Two primary drivers are currently debated by scientists. The first is the Alvarez hypothesis, proposed in 1980 by Luis and Walter Alvarez. They identified an unusually high concentration of iridium—an element rare on Earth but common in meteorites—in the K-Pg boundary layer. This theory is supported by the existence of the Chicxulub crater in Mexico, which is approximately 93 miles wide. Drilling in 2016 revealed that such an impact could have vaporized enough rock and gas to alter the atmosphere for years, evidenced by tektites—tiny glass beads formed from melted rock—found in North Dakota fossils.
The second leading theory points to Earth's own internal volatility. Massive volcanic eruptions in India, known as the Deccan Traps, produced enormous lava flows between 60 and 65 million years ago. These eruptions may have triggered large-scale climate change. Some researchers argue the asteroid evidence is inconclusive, suggesting that while the impact was catastrophic, the combination of volcanic activity and gradual environmental shifts likely sealed the fate of the species that could not adapt quickly enough.
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Sources
- Summary by Intellect · source: How did the dinosaurs become extinct?
- Also: Dinosaur - Extinction Causes, Evidence, & Theory | Britannica
- Also: Why did the dinosaurs go extinct?
- Also: What killed the dinosaurs? | Natural History Museum
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