What is a Mass Extinction Event?

Some pretty hardcore things have happened in Earth’s history. Natural disasters have reshaped the landscape, species have risen to the top and fallen to the bottom, and planet-wide extinctions have shaped the course of the future. The latter events are called “mass extinctions,” and they represent significant turning points in Earth’s past. Here’s everything you need to know about mass extinctions.

1. What they are and how they occur.
A mass extinction event is when most of the species on Earth suddenly die out in a very short period of time. Mass extinction events generally occur when environments on Earth change very rapidly and organisms don’t have a chance or the ability to adapt. Both plants and animals can be victims of mass extinctions.

2. Earth’s five mass extinctions.
Scientists have identified five mass extinctions in Earth’s history. They’re named after the geological time period they occured in (and also marked the end of). These mass extinctions, in order of oldest to most recent, were the Ordovician, Devonian, Permian, Triassic-Jurassic, and K-T (or Cretaceous-Tertiary). The K-T mass extinction is probably the most well-known, as it was the one that marked the end of the dinosaurs.

3. Are we in a sixth mass extinction?
Human activities have altered the face of the planet and severely affected other life forms. Because of the effect we’ve had on other species (often negative), some scientists believe we are in the middle of a sixth mass extinction, this one of our own doing. Species have gone extinct much faster than they would naturally thanks to humans. If we truly are witnessing (and creating) a sixth mass extinction, the question is: who will survive it?