One often wonders where life began, how long life has been around for, and what the earth has gone through in it’s 4.6 billion years of existence. We recently picked up a copy of ‘Know’ and couldn’t help but admire the ‘Geological timeline’ section. We’re going to go through what we’ve learnt from it and explain a little of what it means. Without further ado, we present to you, the history of life!
The earth began around 4.6 billion years ago, the first eras being the Archean and Proterozoic, which both lasted 4.5 billion years. That’s two very long periods! Almost all of time on earth was in those two periods, take that in!
Next up is 3 sections to make things easier (thank you to the author Katrina Greenslade for simplifying this for us).
The Paleozoic Era covers 7 periods, from 542-252 million years ago. This period started with Fungi and plants as the C02 levels were huge – they were everywhere. Forests then made all the fossil fuels that we still use now. Soft bodied animals and sea life soon bloomed and then the first ice age happened and wiped out all creations hard work, killing almost all life. They then rallied and sea levels rose with the melting ice. Fishes were everywhere after this and it suddenly got very hot!
Just when the fish were thriving, another mass extinction came around; this was mostly due to changes in the climate and sea levels, new soil and asteroid impacts. Eventually life began again and ‘the age of oxygen’ began, plants died and turned to coal very quickly because there was not enough CO2 (unfortunately the plants pretty much doomed themselves, as their rapid growth caused a major lack of carbon dioxide’), With so many plants there was a huge increase in O2 levels; this oxygen cooled the Earth and it wasn’t long until another ice age began, which was followed by the most devastating mass extinction the world has ever known… which was followed by the most devastating mass extinction the world has ever known. Everything warmed up and the ice faded, but oxygen levels went from 35% to 15%... If you put that in perspective of our current level of 21%, it’s no surprise that 96% of species died out. This means, however, that we all evolved from the tiny 4% of creatures that managed to survive.
Now into our next era, the Mesozoic Era.. After the awful mass extinction, everything took some time to recover. In the Triassic period, it was very hot, very frosty and very empty – which left a lot of room for evolution. This is where the first creatures that we refer to as dinosaurs came by (late Triassic).
Pangaea also famously began to break apart. A little-known-about extinction happened at the end of the Triassic period, killing around half of life but mostly hitting marine life with 96% of them dying out. This was due to climate changes, basalt eruptions (caused in most part by the Pangaea shift), methane from the sea floor and asteroid impacts. It was also the only known mass extinction of insects ever! Where was this in the movies?
It appears that life began recovering quickly from mass extinctions. Life flourished and before long, the world was full of the most diverse organisms we’ve ever known. This period was famously referred to as ‘The Age of the Dinosaurs’ or The Jurassic Period – there’s a reason why they called Jurassic Park after that particular period (though… weirdly enough the T. Rex didn’t actually live in the Jurassic period. It lived in the late Cretaceous period. Getcha facts right Spielberg). We saw the first birds and famous dinosaurs. There was very little life to begin with so there was little competition among species – lots of food and space, so they survived very easily. Our current ocean floor was also formed.
Thankfully this period did not end in another extinction, though, we all know what is coming… The warm Cretaceous period had no ice in the polar regions, with much of the world underwater. More dinosaurs began forming, and the big boys came out of the forests – the largest dinosaur known so far arrived at this time.
Then followed the famous death of dinosaurs. The decline began with falling sea levels and basalt eruptions and was finished off by the huge asteroid. Around ¾ of life became extinct. Thankfully this was the last mass extinction
s that Earth has experienced so far.
After this, the Cenoic era began. When the reptiles died, mammals flourished. Lots of new creatures appeared over time and sea levels rose again.
The world soon got very hot, the Himalayas were formed as India pushed against the Eurasian continent. Global cooling soon began and the climate shifted, fewer forests and more open areas spread around the world; apes appeared and Kelp forests became a thing – an extremely productive ecosystem. Earth began looking very similar to how it looks now. The next period, 2.6 million years ago, brought multiple ice ages, whilst the ice was churning we were evolving.
And that’s where we are now! It began when the glacier’s diminished, so while we’re technically still in an ice age, it’s just in an interglacial phase. To think we’ve only really been around for thousands of years… Compare that to the 4.6 billion years the earth has been around! Science is wonderful.
This is just one of the topics that Katrina features. She tells us the differences between a crocodile and an alligator, tells us of traditional and modern anniversary gifts and what the most poisonous plants in the world are! ‘Know’ is bursting with interesting facts and features, and with Christmas coming up, it really is the perfect stocking filler for those with a thirst for knowledge! Grab yourself a copy, HERE!
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