First and foremost - science is cool, but it’s even cooler when you start it with an applicable song. (I won’t do that each time. Just this time.)

The precambrian lasted for nearly 4 billion years, it’s by far the largest geological time period yet we pretty much know the least about it. (And I also don’t want to get focused in on it, so this is a pretty simplistic post about it.) The earth went from being a ball of random matter and particles at that time to becoming a much more delicate unit with the first signs of life.

Hadean

We start the Precambrian period with hell, literally. The first time period within the precambrian is the Hadean which translates in Greek to “unseen” or “hell“. In the 20th century geologists identified a few rocks from the Hadean period in Greenland, NW Canada and Western Australia. The oldest rock formation currently known to geologists dates back to about 3.8 billion years ago originating from a volcanic dike, and can be found in Isua greenstone belt.

Even older than these are individual crystals in sedimentary rocks found in Western Canada and Western Australia, these date back to about 4.4 billion years ago. This 4.4 billion year mark would be the beginning of the Hadean era, as it is the first era and simply starts, well, when the earth starts and ends at about 3.8 billion years.

It is during this period that the lunar cataclysm occurred, around 3.8 - 4.1 billion years ago. A period when the earth was being bombarded by a large number of craters that are believed to have formed the moon. The dating of lunar samples indicate that most impact melt rocks formed in an extremely “small” amount of time. (Please remember, when I say things like “small” in these posts, I mean …small on a geological scale.)

The earth was formed by material that had a large quantity of water, after some escaping from the earth’s radius, 40% of the current size, the water molecules would have been retained to form the waters - which as we’ll see, and most probably already know, is the most important factor of our earth’s history. But the impact that happened, where in which the moon was created, would have created a rock vapor atmosphere around the planet which would have condensed quickly leaving behind an ideal center for a C02 atmosphere with hydrogen and plenty of water vapor, make this collision extremely important.

The formation of the moon stabilized Earth’s orbit around the sun and created tides which helped to aerate and cleanse the waters. The heavy atmosphere kept the liquid on the earth, and soon subduction started to occur, removing some of the carbon dioxide and mantle cycles started to appear.

Archaean

The Archaean eon starts at 3.8 billion years to 2.5 billion years ago and contains one of my absolute favorite things prehistory, stromatolites. No one can really *know* how life on earth started, there are a few theories and models about how life can arise, I don’t want to get into it too much - but one theory is that the first simple organisms may have arisen in the underwater hot springs, where there would have been an abundance of heat as well as the chemicals now thought to be needed for the formation of life - methane, ammonia, water, carbon dioxide & monoxide and phosphate.

But anyway it was probably a combination of different things, I’d suspect.. clay, waters, hot springs… etc. Anyway, thin layers of single celled slime covered seabeds and eventually started extracting energy from chemical reactions… and eventually up pops the cyanobacteria which started up some photosynthesis. The bacteria formed mats on the sea floors and started formulating in mounds, which would be the stromatolites, the earliest 0f all fossils dating at around 3.5 billion years ago.

Coming to the end of the archaean there may have been tectonic activity much like that of current day earth as there is evidence of volcanic activities and intracontinental rifts. And the continents finally stabilized at the end of this period 2.8 billion years ago, but the rock that formed the cratons then only makes up about 7% of the world’s current continents.

Proterozoic

The Archaean can be remembered for marking the beginning of the evolution of all life, the proterozoic simply saw this period go from simple bacteria into complex plants and animals of the sort that we would actually recognize today. The proterozoic is broken into 3 separate time periods which are then broken into even shorter periods.

1. paleoproterozoic
   1. siderian (2.5 bya)
   2. rhyacian (2.3 bya)
   3. Orosirian (2.05 bya)
   4. Statherian (1.8 bya)
2. mesoproterozoic
   1. calymmian (1.6 bya)
   2. ectasian (1.4 bya)
   3. stenian (1.2 bya)
3. neoproterozoic
   1. Tonian (1 bya
   2. Cryogenian (.85 bya)
   3. Ediacara (.63 bya)

The siderian’s most important event that can now be observed in banded iron formations was the great oxidation. Lots of photosynthesis and more places of carbon to be stored/buried in the sediements resulted in a more oxygen rich atmosphere. What quickly followed 2.4 bya was the Huronian glaciation lasting until 2.1 bya. After this glaciation the atmosphere was able to become oxygenic resulting in the beginning of the first complex single celled life 1.6 bya, also known as eukaryotes. Unlike bacteria, the prokaryotes, each eukaryotic cell had a separate nucleus that contained DNA at the very center. The first eukaryote fossil is the acritarch which can be found inside of sedimentary rocks dating as far back as 1.5 bya all the way up to present day production.

At 1.2 bya the supercontinent that is always ignored in geology and geography classes formed, Rodinia.

And the time period come to a close with a giant ice age turning the world into a snowball at .85 bya, it melts and the world starts to flourish with vendobionta along side the first sponges and trilobitomorphs. Fossils from 600 million years ago are very rare, and it is next time that I’ll start talking about those that appeared in the palaeozoic era - the era when we see the evolution of large, complex land animals and really cool marine creatures.