Most people (perhaps I’m being a little optimistic, but hey) these days are familiar with basic tectonics and have a vague notion of what Pangaea is. The thing is, Pangaea existed only around 225 million years ago, but the history of Earth goes well over 4 billion years before that. So, aren’t you curious as to what on earth (quite literally) was going on for all that time?
It is estimated by geologists that the first continental crust formed about 4 billion years ago (now referred to as bya because I’m lazy), near the end of something called the Hadean eon (4.5-3.8 bya). By 3.7 bya there was a substantial amount land but still less than 10% of what we have today. Amazingly, some of the rocks that were formed during this period are still present today. Relics of this time (and later) are known as cratons, there are plenty of them around but some of the most spectacular are in Canada where there are tonalite rocks dating 4.0 bya and in Greenland where they’re just behind and 3.85 bya.
Ok, so we have our first bits of land, and of course during this time the Earth’s tectonic plates still moved, subducted and created crust in the same way they do today. By 3.6 bya this lead to the formation of the first supercontinent, Vaalbara, so named for the cratons that composed it. It was made up of two separate cratons which now reside in southern Africa (Kaapvaal) and western Australia (Pilbara). No, I don’t know who decided to call them that. We can tell they used to be together because of the incredibly similar lithological and paleomagnetic structures and sequences in both areas, which have obviously been carbon dated to around this time.
Again through tectonic movements, Vaalbara begins to separate at around 2.8 bya. The continental crust continues to grow in size until 2.7 bya when the cratons come together as another super continent with another silly name - Kenorland. Are you beginning to see a pattern here? It’s called the supercontinent cycle and basically is the quasi-periodic coming together and dispersal of the Earth’s continental crust. This process is inevitable given that the Earth is a sphere and the plates are constantly in motion - there is going to be a collision at some point. When they do collide, the immense force and pressure at some point creates a new plate boundary which forces them away from each other again. This happens over and over again and the continents are constantly reconfiguring themselves.
Anyway, back to the story. Kenorland breaks up around 2.1 bya and by this point there are quite a few significant land masses floating around, and by significant I mean continents in their own right, not just tiny cratons. There’s Ur (3.0 bya), Atlantica (2.0 bya) and Nena (1.8 bya). During the formation of Nena, from a previous continent Artica, in 1.8bya the continents came together again as Columbia, almost certainly named after it’s squeaky tap-dancing counterpart in the Rocky Horror Picture Show. Columbia further developed by 1.5 bya into the biggest continent, yet Rodinia and is probably the best known supercontinent other than Pangaea.
It is important to remember at this point there is absolutely no life on land as the Earth’s atmosphere is far too hostile and there is basically no oxygen for organisms to survive. There is however a rapidly growing plethora of species in the oceans, even multicellular organisms and primitive invertebrates. These have been evolving since around 3.5 bya first as single cellular organisms and eventually to eukaryotes and then invertebrates. It was only after the break up of Rodinia around 750 million years ago (mya) and huge global cooling that the rapid evolution of primitive life forms began start at the beginning of the Cambrian period.
After the break up for Rodinia the continents came back together fairly quickly in 600 mya as Pannotia, which was basically the same landmass but just organised in a different way. Again, it breaks up only around 100 million (500 mya) years later into Gondwana and a handful of other continents which will eventually become Laurasia. The continental pieces continue to float around coming closer and closer to what we know as Pangaea. By now it is the Silurian (420 mya) period and algae and bacteria and altered the atmosphere, mainly in the Ordovician period enough for life to start developing on land. Hooray!
Finally, 300 million years ago Pangaea begins to come together. By 225 mya it is a fully formed super continent and it is the dawn of the Age of the Dinosaurs in the Triassic era. Life has come a long way in since the Silurian…they grow up so fast. The rest, as they say, is history. Of course, I could, and would love to, go into detail on the rest of it but I think I’ll save that for another piece. This was intended as a brief history of Earth and life before Pangaea only. Hope you enjoyed this :3