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Geological History

"Huts" by Christina Mackie outside the Tate Britain

This article is both a brief outline of the geological history of Britain, and perhaps more importantly a history of how people have looked at geology. Although geology might seem rather academic, there have been times when the subject has been hugely emotive. Geology has quite literally changed the way people look at life. The rock beneath our feet has always been a metaphor for the final solidity we can rely on. It was nineteenth century geology investigation that contributed to a changed world view where apparently solid rock beneath our feet began shifting and changing all the time.

The ancient Greeks, for all the variety of their views, had a few general assumptions that helped them get close to understanding the reality of geology. They believed that time was infinite, and that the Earth changed under the force of weathering. Erosion is mentioned in The Iliad, written sometime between the twelfth and the eighth century BC. Ovid tells us that Pythagoras (590 - 510BC) believed that solid earth could be changed into sea, that seashells can be found lying far from the oceans' waves, that plains can become mountains, and mountains can be levelled into plains. But then with the Roman Empire's collapse between the fifth and seventh centuries, Europe slipped into chaos. In AD642 the library at Alexandria, the ancient world's finest collection of knowledge, was destroyed on the orders of Omar Caliph. For many centuries afterwards the view of a changing earth was replaced by a view dominated by Christianity where the earth was created as it is and has never changed. Given the instability of life in Europe at this time, perhaps people needed this kind of outlook.

 

A revival in learning began around 1250. Between 1200 and 1225 Aristotle's full texts were recovered and translated. The mid fifteenth century saw the invention of printing, and America was discovered in 1492. It seemed that people were now more ready to explore, both inwardly and outwardly. Leonardo da Vinci (1452 - 1519) clearly had modern views on erosion, but had to keep his views secret to avoid upsetting the Church. The religious view of an unchanging world still had powerful influence. In 1654 Bishop Usher published his considered view that the Creation took place on 23rd October 4004BC, and Noah's flood took place from 7th December 2349BC to 6th May 2348BC. Many erosional landscape features were explained as evidence of Noah's flood. Usher's creation date was incorporated into the King James Bible in 1701, and afterwards became accepted almost as scripture itself. The notion of Noah's flood explaining land forms persisted into the nineteenth century. This was inspite of the fact that there were always some writers who understood erosion. Palissey (1510 - 1590) and Agricola (1494 - 1555) had modern views of erosion. In England, William Bourne, a mathematician, innkeeper and navy gunner at Gravesend wrote a book in 1578 which described coastal erosion in modern terms. Interestingly Shakespeare, who referred to the Earth as only a few thousand years old in Hamlet, writes elsewhere of an eerily modern conception of geology. In Sonnet 12, written during the 1590s, he says:

 

When I have seen the hungry ocean gain

Advantage on the kingdom of the shore,

And the firm soil win of the wat'ry main,

Increasing store with loss and loss with store;

When I have seen such interchange of state,

Or state itself confounded with decay,

Ruin hath taught me thus to ruminate -

That Time will come and take my love away

 

In the seventeenth century the debate continued. Either erosion had been caused by Noah's great flood, or erosion was seen as not happening at all. This latter view was held, strangely, by John Woodward who endowed the chair of Geology at Cambridge.

 

View from the tower of York Minster

It was towards the end of the eighteenth century that geology finally became more recognisably modern, through the work of William Smith and James Hutton. In 1760 James Hutton presented a modern geological view to the Royal Society of Edinburgh in The System of the Earth, it's Duration and Stability. Then in 1794 one of the great ironies of history occurred when mining engineer William Smith used the tower at York Minster to prove that the old religious world view of an unchanging Earth was incorrect. Smith had been observing through his work in mines how rock sits in layers, and how different layers possess characteristic fossils. He began to think that the layers, or strata, were formed at different times, and might provide a record of earth history. Unless land had been disturbed by violent geological forces, rock layers would become progressively older the deeper they sat in the earth. It was the view provided by York Minster tower that finally allowed Smith to confirm this theory. Looking out from the tower in 1794 he realised that British rocks are tipped towards the south east. Forces of erosion would generally flatten out this tipped landscape, revealing older rocks in raised western areas and younger rocks in lower land in the east. Smith could see a great swathe of land from the top of York Minster tower, and with his geographical knowledge, he realised the rocks were getting older as he looked northwest. Smith then went on to create the first geological map of Britain which was published in 1815. So a cathedral tower, an expression of a school of thought which saw the world as unchanging, provided the view that allowed William Smith to confirm that the world is changing all the time. Charles Lyell published his Principles of Geology in 1830, and the new view was established. Charles Darwin had a copy of Principles of Geology with him on HMS Beagle, sailing on the voyage that would eventually lead to the theory of evolution.

Many felt uncertain in the new mutable world revealed by geology. And yet a kind of stability was also revealed, a breaking down balanced by a building up in endless cycles: or as Shakespeare had put it in the sixteenth century: "Increasing store with loss and loss with store."

 

A three hundred and fifty million year old fossilised tree from Glasgow, displayed outside the Natural History Museum

The geology of Britain is extremely varied, but you can follow its broad outlines by remembering what William Smith saw from the top of York Minster tower. As you go west you are travelling back in time. In the extreme south east there is land formed in the last few thousand, or even few hundred years. Moving a little further west you will find the chalk down-lands, created between 60 and 135 million years ago in bright tropical seas during the time of the dinosaurs. Driving over the chalk downs of Kent or Wiltshire the road runs over what is in effect a huge fossil formation, made up of shells of tiny sea creatures called foraminifera. If you visit the Natural History Museum in London you can see a big Diplodocus skeleton in the main hall. This huge fossil is rather insignificant compared to the fossils which make up the downland of southern England. Then to the west of the chalk are red sandstones. This is what's left of the Permian desert world dating to about 250 million years ago. During the Permian era all continents of the world were combined in one vast lump, known as Pangea. This huge land mass created a very extreme climate. Once the journey reaches Wales you are back in the forests of the Carboniferous period 350 million years ago, when trees were the main form of life on land. Carboniferous trees grew in vast swamps, and their remains form the coal seams of Wales. If you continue to the extreme west of Wales, to St Davids for example, you will be walking on rocks laid down in oceans of what is called the Precambrian period, over 500 million years ago. At this time life was confined to the seas, and many fossils of ancient sealife have been found in the rocks of west Wales.

 

 

 

The Carboniferous, as recreated at the Evolution House, Kew

Geology of course is everywhere, and there is no need to go to specific places to see it. However, there are locations where geology is particularly striking and easy to see. At Alum Bay on the Isle of Wight rock strata are famously arranged in vertical coloured bands, like books on a shelf. Show caves such as Cheddar Gorge in Somerset and Kents Cavern in Devon are a great way in which geology can be experienced in a dramatic setting. The extraordinary geology of the Dorset and east Devon coast has led to this area being designated Britain's first natural World Heritage Site. The site is known as the Jurassic Coast, and along its ninety five mile length there is a complete geological record of 185 million years. There are also museums dedicated to geological history, such as the Sedgwick Museum, and the Natural History Museum. The Evolution House at Kew Gardens has a walk through display where past ages and plants which have produced today's geology are recreated. The importance of geology in influencing the industrial and economic fortunes of Britain can be explored at the Museum Of The Gorge at Ironbridge Gorge in Shropshire.

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