The Paleoproterozoic Era

 Next up is the Paleoproterozoic Era, which spans from 2,500 to 1,600 million years ago. It is the first of 3 sub-divisions (era) of the Proterozoic Eon. It is the longest era of the Earth’s geological history, and is divided into 4 periods, which we will look at later. During this era, the continents first stabilized.

Paleontological evidence suggests that the Earth rotated during this era at a speed that produced days that were 20 hours long, which would have meant a year would have about 450 days long.

It was during this era that the atmosphere and shallow seas saw a great increase in free oxygen, thanks to all that cyanobacteria that had been pumping out oxygen as a waste product for so long. Before that, almost all existing lifeforms were anaerobic, meaning they did not require oxygen. In fact, free oxygen in large amounts is toxic to most anaerobic organism. Therefore, the majority of the anaerobic lifeforms died when the atmospheric free-oxygen levels soared. This was the first major and possibly the most significant mass extinction event, and is called the Great Oxidation Event.

But this was not just a time of death. Many eukaryotes lineages have been approximately dated to the Paleoproterozoic era. Eukaryotes consist of cells that have a nucleus enclosed within a nuclear envelope. To the best that I can remember my high school biology, that would mean that most plants and animals are eukaryotes. It is currently accepted that there are 3 domains of life on Earth, and the eukaryotes are one of them. Bacteria and Archaea are the other two. Neither of these types of life have cells with a nucleus within a nuclear envelope, and I think neither one of them gets large enough to be seen with the naked eye.

During this era, a number of continents collided, creating mountain belts and basins. This happened so often that it led to the assembly of the supercontinent named Columbia (or Nuna, depending on who you talk to).

Now, in doing my research about the Paleoproterozoic Era, I chanced upon a phrase called The Boring Billion. Believe it or not, that sounded interesting, so I did a little more digging (so to speak) and found that it referred to the time period between 1.8 and 0.8 billion years ago, which spans the middle of the Proterozoic eon. It would have just been starting when this era was ending, but I’ll mention it here and hope it comes up again when we get to the next era, so I can study it in more detail.

The Boring Billion section of time was characterized by a fair amount of tectonic stability, climatic stasis, and stalled biological evolution. Supposedly, it was bordered by 2 different oxygenation and glacial events, but the Boring Billion itself had very low oxygen levels and no evidence of glaciation.

Well, no doubt about it, the world is really beginning to shape up into the Earth we know. But I’m not quite ready to move in.

 

https://en.wikipedia.org/wiki/Paleoproterozoic

https://en.wikipedia.org/wiki/Boring_Billion

https://en.wikipedia.org/wiki/Eukaryote