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

Most alarmingly, these statistics indicate that we are currently in the midst of a sixth mass extinction—a mass dying-off of species.

Read more on Literature

The reality of the current mass extinction—and the sheer volume of animals close to or on the brink—is cause for great alarm.

Read more on Literature

"We tend to think of evolution as constant change, but here's an example of a behavior that worked so well, it stayed the same through multiple mass extinction events."

Read more on Science Daily

For years, many scientists have warned that Earth is undergoing another mass extinction, with species disappearing faster than ever before.

Read more on Science Daily

The researchers argue that predictions of an ongoing mass extinction may rely on oversimplified or outdated assumptions.

Read more on Science Daily