James Hutton ： Deep Time

This is a story of James Hutton, the father of modern geology and the development of deep time. Before 1788, the consensus in science was that the world was 6,000 years old. In fact, the precise date of creation had been determined by Bishop Usher of Ireland through a scholarly analysis of the Bible to the October 22nd, 4004 BC. Even Sir Isaac Newton, the father of modern science, had repeated the analysis with similar results. At the University of Edinburgh, a professor who had known Isaac Newton instilled in the young James Hutton Newton's rules for scientific study, including if observations or experimental evidence conflicts with theory, then the theory must be changed to fit the facts. After completing his medical studies, Hutton turned to farming, which gave him a chance to examine the earth's surface in detail. Later in life, he moved back to Edinburgh where he became involved in the management of building the 4th and Clyde Canal, both an application of his geological knowledge and a chance to study more of the surface of the earth. Not far from Edinburgh Castle in Holyrood Park, James found what is now called Hutton's Section, the most famous geological site in Edinburgh. The reigning theory at this time proposed that rocks had precipitated from the early ocean that once covered the earth, but here Hutton found a slab of sedimentary rock that had been torn away during the injection of magma from below, and then hardening to form the dolerite structure known as Salisbury Crags. This was a clear example of the junction between the younger, igneous rock and the much older underlying sedimentary rocks. This evidence that some rocks must have formed from molten liquids was a direct challenge to the reigning theory. But Hutton needed to find proof that the earth was really old in order to convince any of his associates. To this end, Hutton and two of his closest associates set out in a boat to explore the coast of Scotland, and it was at Siccar Point that he found what he was looking for. Here we follow a trail dedicated to Hutton with our geologist guide Angus Miller. It's so important for Hutton because it was so much better than anything he'd seen before. So what we've got is a grey wacky sandstone and right hand side you can see that the layers are standing up on end and that is because after they were formed they were subject to plate tectonics. They were folded up and shoved up into these very steep sided layers and then erosion had taken hold and it started to work away the grey wacky layers and then conditions changed and the red sandstone started to accumulate here. So there's still red sandstone lying on the left hand side all the way across the much flatter lying layers. The lower parts of it has got barnacles on it. Darwin would have appreciated that I'm sure if he ever came here. So the colour changes but it's the red sandstone and what Hutton realised as well when they sought here was that there was a variation in the surface of the unconformity that the grey wacky when it was being worn away was subject to natural forces and the harder stuff was surviving better than the softer stuff. So there was actually an existing topography that was buried by the red sandstone accumulating on top of it. So way over to the left hand side you see more of the grey wacky just sticking up through the layers of red sandstone and that's one of the things that James Hall picked out in his sketch that the harder layers stick up. The other thing that Hutton saw here for the first time and was very pleased about was the lowest layers of the red sandstone have got chunks of the older sandstone embedded in them. So this is important for him in terms of showing the progression of different episodes that have formed this series of chapters of the story. It didn't all happen at once. There was no need for any for a higher power he described. No need for a higher power to explain this. It could be explained by the processes of the earth. You just needed time and so he picked out the fact that there would have been the original accumulation of the grey rocks and then deformation of them. So they've been squashed from north to south and like compressing a carpet so it built up into these whole series of steep-sided folds. So that's set two and then the next chapter is erosion of that existing rock. So it starts to wear away and we get a dry land here with ridges and valleys and then step four is the accumulation of the red sandstones and most of the red sandstone is derived from material that's come from the north. So the time it was forming on the horizon to the north would have been proper mountains. You'll go through the highlands, you'll see the highlands they're impressive but they're not high and if we go back 400 million years to when the red sandstone was forming that would have been a towering mountain range, a Himalayan scale mountain range on the horizon there and that was eroding and material was being swept down here so it started to accumulate here. And then stage five is that the red sandstone itself has had a slight tectonic deformation as well not nearly as severe as the earlier rock but it's tilted out towards the sea at a low angle. And then finally we're in stage six, chapter six of the story, erosion is going on. It's been going on here for millions of years and it's stripped away what was a huge amount of red sandstone that accumulated above this point. It gradually works its way, the sea's come in here and has helped in the erosion and we're at the stage now where the very last bits of the red sandstone are clinging on on top of the of the grey and it's still visible. So this was even certainly one of the most significant events in the development of geological thought the day the three of them came here in 1788. Playfair was a person that really described it particularly well. We're carried back in time to when the rock in which you stood was at the bottom of the sea and the sandstone before it was yet beginning to be deposited. The mind seemed to grow giddy by looking so far into the abyss of time. So they got it, Playfair got it, Hutton jumped around in the rocks and told them the story and Playfair, the light bulb moment for him, he saw what Hutton was talking about, he understood the immensity of it and this bit at the end that they said, they became sensible how much further reason may sometimes go than imagination may venture to follow. So you would say really that this was the scientific facts presented by Hutton, the series of events, it was unbelievable but it was backed up by the evidence. After the trip to Sicker Point, Hutton's paper was published in the Proceedings of the Royal Society but has worked and become widely known until after his death when one of his companions on that trip, John Playfair, publicized Hutton's ideas in a book entitled Illustration of Hutton's Theory of the Earth. Charles Lyle, who was born eight months after Hutton died, went on to expand on Hutton's ideas and wrote The Principles of Geology which became the standard geology text for the next 100 years. Charles Darwin brought a copy of Lyle's book along on the voyage of the Beagle and this helped shape his thinking with Hutton's theory allowing the time necessary for natural selection to work. Back to the initial question, how old is the earth? Hutton's answer was, we find no vestige of the beginning, no prospect of an end. As science progressed, we have developed the tools to estimate the earth to be 4.5 billion years old. We have taken the walk to learn about Hutton and how he began to convince the world about the enormity of time and the great influence deep time had on the development of science.