The Chicxulub Impact: What Killed the Dinosaurs 66 Million Years Ago

A 10-kilometer asteroid hit the Yucatán Peninsula and triggered a cascading apocalypse — not just the impact itself, but the aftermath. This is the K-Pg extinction event (formerly called K-T), and it killed about 75% of all species on Earth, including all non-avian dinosaurs.

What Happened

An asteroid roughly the size of Mount Everest (called Chicxulub, after the impact crater) struck what is now Mexico at about 20 kilometers per second. The energy released was equivalent to billions of atomic bombs. The impact created a crater 180 kilometers wide and vaporized rock, sending a shockwave outward that flattened forests thousands of kilometers away.

Why It Killed So Much

1. Immediate thermal pulse — the impact released such intense heat that forests caught fire within 1,600 km of the impact site. A global firestorm followed.
2. Impact winter — dust and soot from the impact and fires blocked out the sun for months to years. Temperatures plummeted. Photosynthesis stopped. Plants died. Herbivores starved. Then carnivores starved.
3. Acid rain and chemical chaos — sulfur from vaporized rock created sulfuric acid rain, poisoning water sources and soil. Ozone depletion flooded the planet with UV radiation.
4. Tsunamis — the impact triggered massive ocean waves that devastated coastal ecosystems.
5. Long-term climate disruption — after the dust settled, CO₂ and soot in the atmosphere caused rapid warming, then cooling, then more warming. The climate whiplashed for decades.

Why Some Things Survived

Small mammals, birds, crocodiles, turtles, and amphibians survived because they required less food, could shelter in burrows, or had other survival advantages. Birds are, technically, living dinosaurs — the lineage never died out. Large animals (dinosaurs, pterosaurs, large marine reptiles) could not survive the starvation period. This is why we have sparrows today but not Triceratops.

Pro tip: The smoking gun for this theory came in the 1980s when scientists found iridium (rare on Earth but common in meteorites) in the K-Pg boundary layer worldwide. Before that, scientists thought dinosaurs had just slowly faded away. The impact hypothesis was radical at the time — now it is ironclad.