Simplified Geological Timeline
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Simplified Geological Timeline

The earth’s history is marked by long periods of stability punctuated by sudden changes (on a geological scale) and often catastrophic events (for the ecosystems in place). This history is told by fossils, rocks, and indicators that tell us about past climatic conditions. This geological timeline is a good illustration of this history; it is divided into chapters.

The earth’s history is marked by long periods of stability punctuated by sudden changes (on a geological scale) and often catastrophic events (for the ecosystems in place). This history is told by fossils, rocks, and indicators that tell us about past climatic conditions. This geological timeline is a good illustration of this history; it is divided into chapters.

Eons are the largest subdivisions, and there are four of them: the Hadean (earth’s early childhood), the Archean (the appearance of life), the Proterozoic (the time of multicellular organisms), and the Phanerozoic (meaning “visible life”).

The eons are divided into eras. The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic, meaning “ancient life,” “middle life,” and “new life,” respectively. We have been in the Cenozoic era for the past 66 million years, since the famous mass extinction of the dinosaurs and other forms of life.

The Cenozoic is in turn divided into periods: the Paleogene, Neogene, and Quaternary. The Quaternary began nearly 2.6 million years ago and continues to this day. It is characterized by a succession of five major glaciations that, at their maximums, spread a thick layer of ice over large portions of North America, Eurasia and Patagonia. During these events, sea level was up to 120 metres lower than it is today. The evolution of the human species and its great prehistoric migrations out of Africa took place during this period.

Finally, the Quaternary is divided into two epochs: the Pleistocene and the Holocene. The transition between these two periods took place at the end of the last glaciation 11,700 years ago. The rise of civilizations took place during the Holocene. However, more and more scientists maintain that the influence of humanity on the earth’s system is so great that a new era should be added to the Quaternary, or even a new period to the Cenozoic. If this idea becomes accepted, it will likely be called the Anthropocene, meaning “the epoch or period of humans.”

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