With all that we know about the Earth, its history, and what it provides for us, we can gather that there have been five mass extinctions within the past 440 million years. Today, we are currently living in what we know as the sixth mass extinction.

Mass extinctions like the ones in the past can take tens of thousands of years, but geologically, this is a short period of time. Each of the five mass extinctions has had its "specialty age" of what went extinct. Each of the extinctions, for the most part, also has its own reasoning as to what caused it.

    The first mass extinction that we know about was the Ordovician-Silurian which happened 440 mya. This is known as the "age of trilobites" where half of the genera of trilobites and benthic species went extinct. This was caused by a quick climate shift from greenhouse warming to the ice house.

    The second mass extinction was the End-Devonian which occurred 370 mya. This extinction is known as the "age of fishes" where 1/5 of bony and cartilaginous fish went extinct. This was caused by land plants evolving and expanding which lead to the Earth cooling because of decreased atmospheric CO2.

    The third mass extinction was the Permian-Triassic which occurred 250 mya, this was the worst mass extinction that we know of. This era is known as the Great Dying and 90% of species went extinct, 95% of those being marine species. The cause of this extinction is still unknown but there are theories about an asteroid impact or methane release being the cause.

    The fourth mass extinction was the End-Triassic which happened 200 mya. This is known as the "age of amphibians" where 1/3 of marine species were lost and most large amphibians went extinct. The cause of this extinction is also unknown but the theories are the same as the Great Dying era.