mass extinction

1. The extinction of a large number of species within a relatively short period of geological time, thought to be due to factors such as a catastrophic global event or widespread environmental change that occurs too rapidly for most species to adapt. At least five mass extinctions have been identified in the fossil record, coming at or toward the end of the Ordovician, Devonian, Permian, Triassic, and Cretaceous Periods. The Permian extinction, which took place 245 million years ago, is the largest known mass extinction in the Earth's history, resulting in the extinction of an estimated 90 percent of marine species. In the Cretaceous extinction, 65 million years ago, an estimated 75 percent of species, including the dinosaurs, became extinct, possibly as the result of an asteroid colliding with the Earth.

2. Compare background extinction

mass extinction

1. Any of several events in the Earth's past in which large numbers of species (in some cases, up to eighty percent) became extinct.

The most famous mass extinction included the destruction of the dinosaurs sixty-five million years ago. (See Alvarez hypothesis.)

Example Sentences

The gallery covering the past 70,000 years is called “Mass Extinction in the Making,” demonstrating how many large land-animal species were wiped out as humans appeared, and warning of extinctions yet to come due to man-made climate change.

Read more on The Wall Street Journal

As we head into our planet’s sixth mass extinction, species nostalgia is understandable.

Read more on Slate

Together, these imported creatures caused a mass extinction; nearly half of New Zealand’s vertebrate species have disappeared since their arrival on the islands.

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The current rate of species decline is so great globally that many scientists warn humans could be causing the "sixth mass extinction" on Earth.

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You’ve heard it before: we’re well into the sixth mass extinction of life on earth.

Read more on Salon