Dinosaurs became extinct about 65 million years ago at the end of the cretaceous period (see what cretaceous dinosaurs were around at this time). About 70% of all animal life on earth died out. Scientists call it a mass extinction it wasnt the first mass extinction in earths history and it probably wont be the last! Having existed for 165 million years, why did dinosaurs die out? There are many different theories about why this happened. We will probably never know exactly what happened, which means that scientists will continue to disagree and come up with different dinosaur extinction theories. Here are some of them:
A massive asteroid hit the earth at Chicxulub on the Yucatan Peninsula in Mexico about 65 million years. The meteor crater is 180 km from rim to rim and scientists have worked out that the asteroid must have been 10 km across. It is thought that the impact would have caused massive damage, including a giant dust cloud which lead to massive changes in the climate. This would have destroyed lots of the cretaceous plants, so herbivorous dinosaurs starved and the meat eating ones were left with nothing to eat either.
Ice Age Theory
Now and again, the earth cools into periods we call ice ages. As dinosaurs were thought to be cold blooded, it would have been hard for them to cope with such cold conditions. For example, if large parts of the planet were covered in ice, then there would have been little or no plants for herbivorous dinos to eat. However, there is no real evidence of an ice age at this time.
There was massive volcanic activity between 63 and 67 million years ago, particularly on the Deccan Plateau in western India. This, again, would have caused a massive change in climate, which dinosaurs would have found hard to adapt to.
It is possible that a disease spread through the dinosaur population causing their extinction.
Competition from Other Animals
Fossils of small mammals have been found from 65 million years ago. It is possible that these small cretaceous animals started to compete with dinosaurs, for example stealing and eating dinosaur eggs. However, no-one is sure whether mammals caused dinosaur extinction, or they thrived because dinosaurs were no longer around.
The number of dinos declined throughout the cretaceous period. Maybe a number of factors contributed to their eventual extinction and they just died out. Dinosaur extinction is a big mystery, as although dinosaurs died out at this time, many species survived, including similar animal types like crocodiles.
Scientist have come up with some strange ideas but none of the theories really explains everything, so we will probably never be sure what happened.