Dinosaur Extinction: What Really Happened

The extinction of non-avian dinosaurs 66 million years ago is one of the most studied events in Earth's history. The evidence now overwhelmingly supports an asteroid impact as the primary cause, though the full picture is more complex.

In 1980, Luis and Walter Alvarez discovered an iridium-rich clay layer at the Cretaceous-Paleogene (K-Pg) boundary worldwide. Iridium is rare on Earth but common in asteroids. This led to the hypothesis that a large asteroid impact caused the extinction.

The smoking gun was found in 1991: the Chicxulub crater, buried beneath the Yucatan Peninsula in Mexico. The crater is approximately 180 km in diameter, formed by an asteroid roughly 10-15 km across traveling at about 20 km per second.

The impact triggered a global catastrophe: a massive fireball, worldwide wildfires, an impact winter from ejected dust blocking sunlight, acid rain from vaporized rock, and potentially decades of disrupted climate. Photosynthesis collapsed, food chains broke down, and about 75% of all species went extinct.

However, dinosaurs were already under stress before the impact. Volcanic activity at the Deccan Traps in India was releasing massive amounts of gas and ash. Whether this volcanism was a contributing cause or merely coincidental remains debated.

Critically, birds survived. As small, warm-blooded, feathered dinosaurs with diverse diets, they were better equipped to survive the harsh conditions. The dinosaur lineage did not end — it continues in over 10,000 species of living birds.