What are the major mass extinctions in earth's history?
The top five popularly referenced major mass extinction events are:
1. Cretaceous-Paleogene extinction event
2. Triassic-Jurassic extinction event
3. Perimian-Triassic extinction event
4. Late Devonian extinction event
5.Ordovician-Silurian extinction event
identified by Jack Sepkoski and David M. Raup. Depending how you measure the impact of extinctions, you could count other events in the top 5.
An extinction event is a sharp drop in the amount of life (as measured by biologically complex lifeforms). In the past 540 million years, 5 mass extinction events have occured where more than 50% of animal species died.