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Proterozoic EON

Sandra

Created on February 17, 2025

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Transcript

Proterozoic EON

Earth's Transformation – From Microbial World to the Dawn of Complex Life!t

Major Event: The Great Oxygenation Event (GOE) (~2.4 Billion Years Ago)

How long did this era last?

The Proterozoic Eon lasted for about 1.96 billion years, from 2.5 billion years ago (Ga) to 541 million years ago (Ma)

What Happened? - Cyanobacteria, the Microbial Superstars Before the GOE, Earth’s atmosphere was mostly nitrogen and carbon dioxide, with almost no oxygen. - Cyanobacteria, tiny ocean-dwelling microbes, had already been photosynthesizing for millions of years. As they absorbed sunlight, they released oxygen as a waste product.

What was the world like? What organisms lived during this time?

Cool Facts!

The Proterozoic Eon (2.5 billion to 541 million years ago) was a time of dramatic changes in Earth's atmosphere, climate, and life forms.
  • Fact #1: Oxygen Was Once a Poison!
Today, we need oxygen to survive, but during the GOE, it was a deadly gas for most life forms on Earth. Imagine a world where "fresh air" was actually a toxic hazard!
  • Fact #2: Ancient Rocks Reveal the Story
Scientists can track when the GOE happened by studying banded iron formations (BIFs)—striped rock layers in old seabeds. These formations stopped forming when free oxygen became common in the oceans!

Atmosphere and Climate

  • Fact #3: The Sky May Have Changed Color!
Before the GOE, Earth's sky might have looked orange or hazy due to methane in the atmosphere. As oxygen levels rose, the sky turned the familiar blue we see today.
  • The Great Oxygenation Event (GOE) (~2.4 billion years ago)
Before the Proterozoic, Earth’s atmosphere had almost no free oxygen. However, early cyanobacteria (photosynthetic bacteria) began producing oxygen through photosynthesis. Over time, oxygen built up in the atmosphere, leading to the GOE.
  • This increase in oxygen triggered a mass extinction of anaerobic organisms that could not survive in an oxygen-rich environment. However, it also paved the way for more complex life forms to evolve.
  • Fact #6: It Was the First (But Not the Last) Oxygen Spike
The GOE was just the first big jump in Earth's oxygen levels. Another major increase, called the Neoproterozoic Oxygenation Event (~800 million years ago), helped set the stage for complex multicellular life.

References:

  • Hazen, R. M. (2008). The evolution of minerals. Scientific American, 319(3), 58-65. Link
  • Hazen, R. M., Papineau, D., Bleeker, W., Downs, R. T., Ferry, J. M., McCoy, T. J., ... & Sverjensky, D. A. (2008). Mineral evolution. American Mineralogist, 93(11-12), 1693-1720. Link