Looking at the Geological Time Scale you can notice that most of the life events take place in the Phanerozoic Eon. It is the eon we currently live in, it is also when most of the multicellular life evolution took place. We will follow that evolution, but first, let’s discuss the basics of the Eon.

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The Beginning of the Phanerozoic Eon

The new eon began with the Cambrian period, more specifically with Cambrian Explosion. To be even more specific, scientists propose the exact boundary between Proterozoic and Phanerozoic. It is marked with the appearance of trilobites (see image below) and reef-creating animals, like corals. Those animals are the first that left body fossils, which we can observe today. Moreover, it was the first time in Earth’s history with such biodiversity and so many new ecological niches. And they were just about to grow even more complex.

However, despite the great life explosions, where the Cambrian is the first within many, Phanerozoic also comes with a few major extinction events. The biggest of them came with the extinction of 96% of life. In conclusion, despite taking up just one-eighth of our planet’s history, Phanerozoic is a dynamic and complex time, and fully understanding it will take many studies and discussions.

trilobite fossil
Fossils of trilobites
Image Courtesy

Eon of Changes

As we already established, the Phanerozoic eon comes with the most significant changes in Earth’s ecology. Those changes were triggered by fluctuations in our planet’s climate and other features. For instance, the Cambrian Explosion might have been caused by plate tectonics. Increasing, and sometimes greatly dropping biodiversity is the result of many processes happening on Earth. Some were triggered by living organisms or continental movement, others came from space. The main point is, neither life or Earth stopped changing, constantly impacting one another.

During the Phanerozoic, those impacts and correlations are especially visible because of numerous niches and revolutions. The history of Phanerozoic is especially important because it led to our own existence. First fish stepped on land, later appeared plants, fungi, followed by the evolution of amphibians, reptiles, and finally mammals. On the other hand, the future of the eon might seem even more important because we’re shaping it.

The Phanerozoic Eon Time Scale

We divide Phanerozoic into three eras. Firstly, the Paleozoic lasted from 541 million years ago, to 252 million years ago. We divide it into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. It is marked by increasing biodiversity on our planet. After that, we have the Mesozoic era, known mostly for dinosaurs. We can divide it into three periods: Triassic, Jurassic, and Cretaceous. And finally, there is the Cenozoic, our current era. The most important part about it is the domination of mammals. There are three periods in the Cenozoic: Paleogene, Neogene, and Quaternary. In short, for the rest of the series, we will discuss a total of twelve periods in three eras, all in one eon.

Phanerozoic time scale
History of life
The time scale of Phanerozoic
Image Courtesy: Sam Noble Museum

The Paleozoic Era

We divide the first, and longest era of Phanerozoic into six periods because of many, revolutionary changes. Its beginning comes with great life explosion, the end with the biggest mass extinction event. Most modern phyla appeared within that era, though a lot of species did not adapt. It also starts with the great breakup of the supercontinent, and ends with the formation of another one- Pangea. At first, climate was changing, to settle in the middle, and then surprisingly changing again, causing mass extinction and many unanswered questions among scientists. Discussing all of the six periods is definitely very extinction because they’re all very different from one another, and each one brings a surprising life turnout.

Pharenozoic Eon
Paleozoic Era
Image Courtesy: sciencephoto

Previous in series: Proterozoic Eon, The Eon of Longest Ice Age!

Author’s Message

I hope that the article gave you a grasp on the eon we live in. If you enjoyed it please share it with family and friends. In the next articles, we will discuss the first period of both the Phanerozoic eon and the Paleozoic era- Cambrian. If you want to contact me, feel free to email me. You can find the address in the author’s section of the page.

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