No one knows why the dinosaurs disappeared for sure.
Dinosaurs of many different types—from small to huge, meat-eating and herbivorous—roamed the entire Earth. They had existed for 150 million years.
Scientists debate many different theories about why the dinosaurs disappeared, and they seem to agree on only one thing:
Something big happened at the end of the Cretaceous period (about 65 million years ago) that altered the environment so that it no longer supported dinosaurs—and many other living creatures.