There are lots of different theories on what wiped out dinosaur life. This happened around 65 million years ago at the end of a period called the Cretaceous period.
Some people think that it was a gradual process where the numbers of different animals, including dinosaurs, got smaller and smaller until they became extinct. They think was because of climate change. The climate was getting cooler. This also led to a fall in sea level so dinosaurs that lived in the sea became extinct.
Other people say that an asteroid hit the earth and that this killed the dinosaurs. The asteroid struck the seabed in Mexico, South America. Scientists have good evidence for this happening and they have found a mineral in the ground in Mexico that is very rare on Earth but more common in meteorites. So maybe that could have come from the event.
There were also lots of volcanic eruptions at the time when dinosaurs became extinct. All of the dust and gases from the volcanoes erupting would have had a big effect on the environment and this may have killed dinosaurs.
Some people also say that birds are actually feathered dinosaurs, meaning dinosaurs aren’t really extinct at all….