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.

Notes

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

Example Sentences

Environmentalists were furious, saying that the plan would lead to the mass extinction of the snake population.

From The Daily Beast

Scientists define a mass extinction as a period of less than two million years in which at least 75 percent of species go extinct.

From The Daily Beast

The Medean world is one out of balance, where over competition leads to mass extinction.

From The Daily Beast