What is a Mass Extinction?
While the name pretty much says it all, an actual, firm definition of what qualifies as a mass extinction is something that biologists continue to debate. There are, however, some common characteristics that we can use to apply to an extinction event that would be considered to fall under the term mass extinction. A significant loss to a large number of species must occur in a short span of time and encompass a wide range of species from many different phyla, habitats and areas across the globe. To be considered a mass extinction the event behind the extinctions has traditionally had to be triggered by a cataclysmic event either terrestrial (such as geological or climatic) or extraterrestrial (collision with large space debris, radiation etc.). There have so far been five extinction events that have been classified as mass extinctions. The Five Mass Extinctions The best known mass extinction is unquestionably the one that occurred during the late Cretaceous and ended the reign of the d
