Mass extinction is, you might (very correctly) assume, a pretty bad thing. I mean, every mass extinction so far has paved the way for a new form of dominant life on Earth, so there are some silver linings. We're here because of mass extinction.
But still, an event where over 50% of the species on Earth have been wiped out can only be called a catastrophe. This has happened on at least five occasions on the geologic time scale. The worst of them was the Permian-Triassic Event over 250 million years ago.
|This chart is the visual equivalent of jargon, but the Event in question is the highest blue peak.|
In that event, up to 96% of the species on Earth were completely eliminated. While there are several theories as to the cause of this disaster, it's nearly impossible to tell for certain what happened. Maybe a large meteor struck the planet or a supervolcano erupted and kicked up enough dust to choke out the majority of life. Maybe a massive, cross-species plague swept through every living thing. Maybe the atmosphere simply changed and most life couldn't catch up.
The point is, shit died. A lot. And that was just the worst Mass Extinction Event. There have been several others. The most famous was the one that finished off the dinosaurs.
|It's not like they were even phoning it in by the end. T-Rex was one of the last surviving species|
The criteria for a mass extinction is that roughly half the species on the planet must have been destroyed within a short period of time. A short period of time on a geologic scale, mind you, means "within a million years or so."
|Or, "Significantly longer than the entirety of human history|
Because "mass extinction" really is just as terrifying as it sounds.