Cretaceous-Paleogene Boundary (65 Million Years Ago)

A rendering of an ocean scene as it may have looked 65 million years ago, when an astroid fell to Earth and triggered a mass extinction event.
Smithsonian Institution

This rendering shows life at the end of the Cretaceous Period, before the impact of a 6.2 mi (10 km) asteroid triggered mass extinctions on land and sea. Dinosaurs are the most famous victims of the extinction at the end of the Cretaceous, 65 million years ago. But they weren't alone. Nearly half of Earth's species disappeared -- including almost 75 percent of ocean species. Evidence indicates an asteroid was to blame. Dust and smoke from the impact blocked sunlight, disrupted photosynthesis and altered Earth's climate. Explore the ancient ocean in an image gallery or in our Ocean Over Time interactive.