Asteroid strike. Artwork of the dinosaur Tyrannosaurus rex fleeing from an asteroid impact. The impact occurred about 65 million years ago at the end of the Cretaceous geological period and was at least partly responsible for the extinction of a wide range of creatures, including the dinosaurs. The asteroid, estimated to be about 20 kilometres across, struck the Earth in the area now known as the Yucatan peninsula in Central America. It threw vast quantities of debris into the upper atmosphere. This debris blocked out the sunlight causing darkness and lowering global temperatures. The remains of this debris is found as a layer in rocks and called the KT boundary.