Merry #draftmas. Not sure why I never published this one. I think I was trying to give it a theme or something and abandoned it.
Permian-Triassic Extinction Event ~ 252 million years ago
Otherwise known as the “Great Dying” this is the big one. Over some thousands of years, 96% of marine species and 75% of the terrestrial species went extinct. Evolution would require up to ten million years to re-establish previous levels of biodiversity. This event is complicated and only partially understood, but can probably be attributed to run of bad luck including a major meteor impact, climate changes cause by volcanic activity, and changes in terrain due to continental drift.
The Great Oxygenation Event ~ 2.3 billion years ago
Contrary to popular belief, life doesn’t need oxygen. Early earth’s atmosphere had none at all. Cyanobacteria, the earliest life, created oxygen as a byproduct of metabolism. Eventually this oxygen built up in the atmosphere with two major consequences: First, it was toxic to the anaerobic bacteria. Second, the conversion of atmospheric methane to carbon dioxide lead to a massive ice age. Combined, these almost killed off the Cyanobacteria entirely. They still exist today in very tiny numbers.
The Holocene Extinction Event ~ Ongoing
Started around 15,000 years ago at the end of the last ice age. Humans are a major contributor to this extinction. Examples of extinctions include mammoths, the famous dodo, the passenger pigeon, and many plants.
[?] Pliocene Supernova ~ 2 millions years ago
There is some evidence that a supernova of a nearby star may have stripped the earth of its ozone layer two million years ago resulting in widespread extinction of some marine life.
The Late Devonian Extinction ~ 360 million years ago
We don’t know much about this one, but it happened slowly and killed about half of all species on earth.
Cretaceous–Paleogene Extinction ~ 66 million years ago
Bye bye dinosaurs.