The intervals of Earth's history are defined largely by their environmental conditions and the effects of those conditions on lifeforms. How do catastrophes relate to environmental conditions, lifeforms, and the intervals of Earth's history?

For example Cretaceous-Paleogene extinction event approximately 66 million years ago led to extinction of approximately three quarters of the plant and animal in Earth. Dinosaurs extinct, but mammals adopt to new conditions and soon becaome one of the largest group in Earth. Temperature drops unnaturaly in Earth's atmosphere. This catastrophe end of the Cretaceous and entire Mesozoic Era and start the Cenozoic Era.