Hello and welcome to the natural history podcast, today we will be talking about deep time. It is not the extinction follow up episode. That is taking a long time to nice weave in to something that makes any sense at all. In fact by the time I finish it, you maybe measuring its release in deep time.
Now you’ve made it this far and I will make a confession, you’ve been thrown you in to the deep end a little, on the past few episodes. Cambrian, Ordovician, Jurassic. Do these names make any since to you? You may recognise the last one.
Well we are going to be jumping around the expanse of geological time a lot, so having a brief understanding of where we are, in time is going to help you keep an idea of what died when, which volcano erupted and when that big meteor did arrive. Fortunately we are heading down a well trodden road, so it should be easy to follow.
So how do the professional tell the time?
Well geologists (The people who study rocks) and palaeontologists ( the chaps who dig up dinosaurs) use something called Deep Time. Deep Time is not a variation on the 24 hour clock, in fact doesn’t move at all. It is more of a time line of earths history, only an extremely long one. If you were to boil an egg using deep time, by the time you came back, it would be fossilised. To get an idea how long we are talking about the earth is 4.5 billion years old. If we where to turn a second in to a year. 1 million seconds is the equivalent of 11 days. 1 billion years, is 32 years. Which means the earth is 144 years old in seconds.
So Deep Time is time a line, a sequence of events that start from the birth of the earth, that goes right up to modern day. Now if take a moment to look at the show notes, or even ask your local search engine, “geological time line” and look under images. you will be greeted by a lot of colourful charts,
they all vary a little, but do the same thing. They start in the bottom left hand corner and work their way up. Then move on to the next column and work your way up again.
So I hope your looking at a time line now, as it is going to make this an awful lot easier.
Got one to hand? good.
The first thing you will notice is that there is not one word of english on it, it is technical gibberish.
The scale is broken up in to four different sections. Eons, Eras, periods and MA.
Starting from the bottom, we have our first eon, the cryptozoic. In this Eon we have the first 4.1 billion years history. The name means invisible life. And going back to our seconds scale that is 131years.
So we have the cryptozoic. The reason for this name is because when the pioneers of geology began to study the rocks and fossils, they noticed a boundary in the records. Rocks older than 500 million years old had no fossils in them. Rock younger than 500 million years were teeming with fossils. The fossil filled Eon is called the Phanerozoic, and that means visible life.
So we have two Eons, the cryptozoic. Which is 500 million years or older and has no fossils in, then we have the phanerozic, which is younger than 500 million years and has all the fossils in.
From the two Eons, we can divide earths history down even more, in to three Eras. The Paleozoic, mesozoic and Cenozoic. There is that word again Zoic – Life. So we have the Paleozoic being old life, mesozoic being middle life and cenozoic meaning- you guessed it! New life.
So the Paleozoic represents ancient life on earth. So ancient we have to go back before the dinosaurs. The Eon lasted nearly 300 million years and in that time we see, life take off. Trilobites, fish, plants, tree, lizards, all evolve during this eon.
It only ends because of the permian extinction, if you remember back, the extinction so vast, it killed 95% of all life on earth. The life that didn’t make it out live, such as the trilobite are classed as the old life or Paleozioc.
The life that took over from the ancients where… the dinosaurs and the Mesozoic is usually what most people think when we talk about natural history. If you are picturing hot jungles and dinosaurs, your on the right track. But as we know, life for the dinosaurs was cut short. When the dinosaurs died out, the mesozoic ended and cenozoic began.
The new life of the Cenozoic, are where the mammals take over. The Cenozoic is the smallest of the Eras, being only 65 million years old, which does sound a lot. But the dinosaurs where around for 180 million years. So double our time and then some.
We then have the last main important section. The periods, and here you may recognise some. The Jurassic should be familiar to you, made famous by Stephen Speilburgs Jurassic park. If you have not heard of the film then you really need to get out more.
There are twelve periods, thirteen if you could the Pre-cambrian. But these periods are the most useful part of the whole scale. They really divide the story of earth in to nice chunks, as each is completely unique. For instance, the Cambrian was a time for life to experiment on how best to design a body ( think Mr potato head) and then we see in the Jurassic period. A time where life, was seeing how far it could physically push a body on vegetables alone. Veganism is not new.
You can keep diving the time line down further in to Epochs and ages. But then we are really getting in to minutia.
Finally you may see the Ma or MA on the time line, is it not time using your mother as a unit of time measuring, but stands for millions of years.
And that is all there is to it really. The most useful part are the periods and that is what most museums, books and podcasts refer to when talking about natural history. You can to some degree disregard the rest.
So I hope you’ve enjoyed, thanks for listening to the natural history podcast.