Dinosaur extinction evidence
Pro Research Analysisby 
Searched over 200M research papers
Evidence for Dinosaur Extinction: Asteroid Impact, Volcanism, and Fossil Record
Asteroid Impact at Chicxulub: Key Evidence
Multiple studies strongly support the hypothesis that a massive asteroid impact at Chicxulub, Mexico, was the main trigger for the extinction of non-avian dinosaurs about 66 million years ago. The global distribution of an iridium-rich layer and impact ejecta at the Cretaceous-Paleogene (K-Pg) boundary matches the timing of the extinction event, indicating a direct link between the impact and the sudden disappearance of dinosaurs. This impact caused immediate catastrophic effects such as shock waves, heat, tsunamis, and a prolonged "impact winter" with darkness and cooling, which devastated ecosystems and primary producers, leading to mass extinction 239.
Role of Deccan Volcanism and Environmental Changes
While the asteroid impact is considered the primary cause, massive volcanic eruptions in the Deccan Traps of India also occurred around the same time. However, climate and ecological modeling shows that volcanism alone could not have caused the global extinction of dinosaurs. In fact, the warming effects from volcanism may have slightly buffered the extreme cooling caused by the asteroid impact, rather than intensifying extinction. Most volcanic outgassing happened before the impact, and only the impact coincided with the mass extinction and major changes in the carbon cycle 39.
Patterns in Dinosaur Diversity Before Extinction
There is ongoing debate about whether dinosaurs were already in decline before the asteroid impact. Some research finds little evidence for a long-term global decline in dinosaur diversity leading up to the extinction, suggesting that the extinction was abrupt and closely tied to the impact event 1410. However, other studies using statistical models and fossil data indicate that dinosaur diversity, especially among large herbivores, was decreasing tens of millions of years before the final extinction, possibly due to climate cooling and ecological competition. This decline may have made dinosaurs more vulnerable to sudden catastrophic events like the asteroid impact 57.
Fossil Record and Direct Evidence
Fossil sites, such as one in North Dakota, provide detailed snapshots of the immediate aftermath of the asteroid impact, including evidence of animals killed by debris and tsunamis minutes after the event. These findings offer some of the most direct evidence linking the impact to the mass extinction . Additionally, geochemical analysis of dinosaur eggshells from South China shows spikes in iridium and other trace elements at the K-Pg boundary, supporting the idea of repeated environmental stress and poisoning leading up to the extinction .
Ecological Stability and Selective Survival
Studies of bird-like dinosaurs show that their ecological diversity remained stable up to the extinction event, with no significant decline in feeding adaptations. This suggests that the extinction was sudden for these groups as well. The survival of some bird lineages may have been due to specific ecological traits, such as a diet of seeds, which allowed them to persist through the harsh post-impact environment .
Conclusion
The current consensus is that the extinction of non-avian dinosaurs was primarily caused by the Chicxulub asteroid impact, which triggered rapid and catastrophic environmental changes. While some evidence points to a gradual decline in certain dinosaur groups before the impact, the abruptness and global scale of the extinction are best explained by the asteroid event, with volcanism playing a secondary, possibly mitigating, role. Fossil and geochemical evidence from around the world continues to strengthen this view, providing a clearer picture of one of Earth's most dramatic mass extinctions 12345678+2 MORE.
Sources and full results
Most relevant research papers on this topic