Mass Extinctions
Main article: Extinction event Marine extinction intensity during phanerozoic eon % Millions of years ago K–Pg Tr–J P–Tr Late D O–S The blue graph shows the apparent percentage (not the absolute number) of marine animal genera becoming extinct during any given time interval. It does not represent all marine species, just those that are readily fossilized. The labels of the "Big Five" extinction events are clickable hyperlinks; see Extinction event for more details. (source and image info)There have been at least five mass extinctions in the history of life on earth, and four in the last 3.5 billion years in which many species have disappeared in a relatively short period of geological time. The massive eruptive event is considered to be one likely cause of the "Great Dying" about 250 million years ago, which is estimated to have killed 90% of species existing at the time. There is also evidence to suggest this event was preceded by another mass extinction known as Olson's Extinction. The Cretaceous–Paleogene extinction event occurred 65 million years ago at the end of the Cretaceous period and is best known for having wiped out non-avian dinosaurs, among many other species.
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