<Ul> <Li> Flood basalt events: 11 occurrences, all associated with significant extinctions But Wignall (2001) concluded that only five of the major extinctions coincided with flood basalt eruptions and that the main phase of extinctions started before the eruptions . </Li> <Li> Sea - level falls: 12, of which seven were associated with significant extinctions . </Li> <Li> Asteroid impacts: one large impact is associated with a mass extinction, i.e. the Cretaceous--Paleogene extinction event; there have been many smaller impacts but they are not associated with significant extinctions . </Li> </Ul> <Li> Flood basalt events: 11 occurrences, all associated with significant extinctions But Wignall (2001) concluded that only five of the major extinctions coincided with flood basalt eruptions and that the main phase of extinctions started before the eruptions . </Li> <Li> Sea - level falls: 12, of which seven were associated with significant extinctions . </Li> <Li> Asteroid impacts: one large impact is associated with a mass extinction, i.e. the Cretaceous--Paleogene extinction event; there have been many smaller impacts but they are not associated with significant extinctions . </Li>

All of the big five extinctions occurred during which eon