As of November 2026, scientists link a giant asteroid to the end of the dinosaurs. It hit Earth about 66 million years ago. As of November 2026, it hit just off the Yucatan Peninsula in Mexico. It left a buried crater more than 90 miles (150 kilometres) across. The crater is called Chicxulub.

In 1980 the scientists Luis and Walter Alvarez proposed that a large asteroid hit Earth and ended the dinosaurs. Rocks laid down at the end of the Cretaceous hold a thin clay layer. It has a lot of iridium. Iridium is a metal. It is rare at Earth's surface but common in asteroids.

The impact sent dust and soot into the air. This cut down the sunlight reaching Earth's surface. It slowed plant growth.

As of November 2026, most scientists accept that an asteroid impact was the main cause of the end-Cretaceous mass extinction. Volcanoes and slow climate change may also have played a part.

As of November 2026, about three quarters of the animals on Earth died out in the mass extinction 66 million years ago. It also ended the flying pterosaurs and many sea animals.

In 1824 William Buckland gave the name Megalosaurus, meaning great lizard, to fossils he described in a scientific article. As of November 2026, it is counted as the first dinosaur to be formally named.

Birds evolved from small meat-eating dinosaurs called theropods. Birds are placed inside the dinosaur family tree. So, scientists say, dinosaurs are not totally extinct.

Words to know

• iridium: rare metal
• extinction: dying out
• proposed: suggested
• crater: big round pit