Proterozoic Eon: Timeline & Facts

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  • 0:00 Timeline of the…
  • 0:21 Snowball…
  • 1:15 Oxygen in the Atmosphere
  • 1:50 Plate Tectonics
  • 2:30 The End of the Proterozoic
  • 2:57 Lesson Summary
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Lesson Transcript
Instructor: Jeff Fennell

Jeff has a master's in engineering and has taught Earth science both domestically and internationally.

The Proterozoic eon was the last of the three eons during the Precambrian supereon. This lesson will cover the unique events that shaped this time period and will also allow you to take a quiz.

Timeline of the Proterozoic Eon

The Proterozoic eon lasted almost two billion years, starting 2,500 million years ago and ending 542 million years ago. During the timeline of the eon, several different events took place, eventually helping to shape the earth as we know it today.

Snowball Earth

During the Proterozoic, the earth had cooled considerably from the previous Hadean eon when the planet was covered by molten lava. Near the end of the Proterozoic, ice sheets were growing towards the equator, and the entire planet was possibly engulfed under a thin layer of snow and ice. Although the cause of Snowball Earth is not understood, there is evidence that ice sheets were present near the equator around 650 million years ago.

Evolution of Life

Life during the Proterozoic began to evolve from simple single cell organisms into more advanced single cell organisms. Eukaryotes, single cell organisms with a nucleus and membrane, evolved from the more simple cyanobacteria. Evolution began to diversify the types of organisms found in the ocean around this time. This increase in abundance of life led to a major change in the atmosphere.

Oxygen in the Atmosphere

Evidence of an increase in oxygen can be seen in the increase of red color in sedimentary rocks by the mineral hematite. Hematite contains iron, and just like any iron, it can rust if exposed to oxygen. Simply put, when iron began to rust, we can determine when oxygen began to be present in the atmosphere. Around 2,000 million years ago, evidence shows that the amount of oxygen in the atmosphere increased. This increase can be attributed to oxygen produced from the photosynthesis by cyanobacteria and eukaryotes.

Plate Tectonics

Plate tectonics were active during the Proterozoic, just as it is now. Between 1,000 - 830 million years ago, plate tectonics pushed the continental masses together to form a supercontinent named Rodinia. Little information is known about Rodinia, but paleomagnetism evidence suggests it to have been positioned in the southern hemisphere.

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