<P> The Great Oxygenation Event was probably the first major extinction event . Since the Cambrian explosion five further major mass extinctions have significantly exceeded the background extinction rate . The most recent and arguably best - known , the Cretaceous -- Paleogene extinction event , which occurred approximately 66 million years ago ( Ma ) , was a large - scale mass extinction of animal and plant species in a geologically short period of time . In addition to the five major mass extinctions , there are numerous minor ones as well , and the ongoing mass extinction caused by human activity is sometimes called the sixth extinction . Mass extinctions seem to be a mainly Phanerozoic phenomenon , with extinction rates low before large complex organisms arose . </P>
<P> The Great Oxygenation Event was probably the first major extinction event . Since the Cambrian explosion five further major mass extinctions have significantly exceeded the background extinction rate . The most recent and arguably best - known , the Cretaceous -- Paleogene extinction event , which occurred approximately 66 million years ago ( Ma ) , was a large - scale mass extinction of animal and plant species in a geologically short period of time . In addition to the five major mass extinctions , there are numerous minor ones as well , and the ongoing mass extinction caused by human activity is sometimes called the sixth extinction . Mass extinctions seem to be a mainly Phanerozoic phenomenon , with extinction rates low before large complex organisms arose . </P>
what is the name of the first extinction
what is the name of the first extinction
Great Oxygenation Event
Great Oxygenation Event