Evidence suggests an asteroid impact was the main culprit. Volcanic eruptions that caused large-scale climate change may also have been involved, together with more gradual changes to Earth's climate that happened over millions of years.

When did dinosaurs go extinct and why?

Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years.

What killed the last dinosaurs?

Dinosaurs went extinct 66 million years ago, apparently as a result of an asteroid impact. ... But the Chicxulub asteroid that rammed into Earth just off the Yucatán peninsula in Mexico 66 million years ago led to the extinction of 75 per cent of all species living at the time.