The Earth 's 4.6 Billion Years Of Existence Essay

815 Words Sep 18th, 2014 4 Pages
Throughout the Earth’s 4.6 billion years of existence, there have been multiple events that mark geographical changes as well as biological changes. Each massive event, (such as a mass extinction) marks the beginning of an eon. An example of an eon is the Hadean eon and the Archean eon. Next are eras, which represents smaller events such as the Paleozoic era. Next are periods which are even smaller such as the Cambrian period. Finally the epochs are the smallest time classifications which subdivide a period such as the Oligocene epoch.
The Archean eon (the second eon chronologically) spanned from 4 to 2.5 billion years ago, and is known as ancient life (The Hadean Eon) Also, the eon is subdivided up into four separate eras: Eoarchean, Paleoarchean, Mesoarchean, and Neoarchean (The Hadean Eon). These categories are separated, but have no real events that really differentiate the time periods (The Hadean Eon). The Archean eon’s roots are: “Archae” (ancient) and “aean” (simple organisms) (The Hadean Eon). Therefore, the Archean eon is an ancient time where simple one-celled organisms thrived (The Hadean Eon).
During the Archean eon, there was a completely opposite atmosphere than today; there was hardly any oxygen (The Hadean Eon). It was during this time that the first simple organisms were created (The Hadean Eon). Most life during this period was bacteria that lived on the water which created an algae-like slime on the surface of the water (The Hadean Eon). These bacteria…

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