Geologist have found the crater of the asteroid that killed off the dinosaurs. It was around 100 kilometers wide. The explosion was so big the sky was covered in smoke and the sun was not visible. It killed off all of the dinosaurs in a time span of a couple hours.

Geologist have also found a boundary in the rocks called the KT Boundary. They can tall judge the age of fossils and rocks by how far they are from the KT Boundary.