The Cretaceous-Paleogene Extinction Event

dinosaurs · mass extinction · 66 million years ago · Earth history

Dinosaurs disappeared. All non-avian dinosaurs went extinct during this event, ending their 165-million-year reign on Earth. However, birds (which are avian dinosaurs) survived and thrived afterward.

Three-quarters gone. About 75 percent of all plant and animal species on Earth died out in this extinction event. Only smaller creatures and certain animals like sea turtles and crocodilians made it through.

Asteroid evidence. Scientists found a thin layer of rock worldwide with unusually high levels of iridium, a metal more common in asteroids than Earth's crust. This suggests a massive asteroid impact caused the catastrophe.

Time divider. This extinction event marked the exact moment when the Cretaceous period and Mesozoic era ended, and the Cenozoic era (our current era) began. It's one of the most important boundaries in Earth's history.

Global boundary layer. Scientists can find the K-Pg boundary, a thin sediment layer from the extinction event, in rocks all around the world. This helps them prove the extinction happened everywhere at once.