What is the Geologic Time Scale? What about the geologic time scale with events? Well, the earth is old, really old. It’s so old that it’s had 4.6 billion birthdays, but it doesn’t like to talk about it.

People called geologists have counted up all the birthdays and made a big fancy chart to help remember them all. It’s called the Geologic Time Scale.

A 4.6 billion years is a long time! Let’s say this represents 100 years, or a human life span. That human life span is only one pixel if we zoom out to 100,000 years. We’d then need 10 of those to get to a million years. We’d then have to add up a thousand of those to get to one billion. That’s a long time!

There are so many Earth birthdays that we have to arrange them into phases, like oh Earth, it’s just a phase. These phases are sometimes called eons. The eons are broken into eras, which are broken into periods and epochs. Geologists are apparently fond of words that start with the letter E.

The first eon is called the Hadean. It’s about half a billion years when the earth is just a hot ball of rock, and the moon is forming. What’s up moon.

Next is the Archean. Everything has chilled out a bit by now, and the continents are forming. This takes a really long time, almost 1.5 billion years and life is starting to form in the oceans. As the Archean is ending, that new life starts farting out oxygen into the atmosphere.

After that is the Proterozoic, which means early life. But really it means very small life. During the Proterozoic we get the first complex cells, and the first things that are made up of more than one cell. The Proterozoic is also very long, about 2 billion years. As the Proterozoic is ending, we get the first plants and the first animals.

The final eon is called the Phanerozoic, which means visible life. It started about 500M years ago with an explosion of new and crazy looking living things, and continues to this day. It’s divided into three eras.

The first era is called the Paleozoic, which means old life. But what it really means is squiggly life, or weird wormy life, and it also means creepy crawly life.

Mesozoic means middle life, but really it means Dino life, or life that goes roar. The Mesozoic ended with a giant asteroid that killed almost everything that went roar.

The third era, the Cenozoic, means new life, but really it means furry life, and flappy flying life. We also got pretty looking things that bloom. There’s lots of different furry and flappy things. There’s things that go blub, things that squawk, and things that go awoo. There’s also new things that go roar, but they're much fuzzier than the old ones.

That’s the geologic time scale! We started with the Hadean, when the earth was still forming, went into the Archean, when we got continents and oxygen in the atmosphere, and ended with the Phanerozoic, when life as we know it now evolved. Some say that humans have changed the earth so much that we’ve entered a new period of geologic time, called the Anthropocene. But more on that next time. Until then, keep it curious.

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