NT8171 : Hutton's Unconformity, Siccar Point
taken 22 years ago, 4 km E of Cockburnspath, Scottish Borders, Scotland

In the 17th century Archbishop James Ussher, a bishop of Armagh, studied the bible in great detail and using the events chronicled therein he calculated that the creation of the Earth commenced at nightfall preceding Sunday, October 23, 4004 BC. Thus it was generally accepted that the Earth was a little under 6000 years old.
James Hutton (1726-1797) was one of the extraordinary men of science and learning who flourished in Edinburgh in the latter part of the 18th century, in a period called the Scottish Enlightenment.
He observed the process of erosion and sedimentation in action, and came to the conclusion that natural processes operated far too slowly for the Earth to be a mere 6000 years old, and he set about looking for evidence.
Near Lochranza in Arran he found NR9352 : Hutton's Unconformity. (An unconformity is a gap in the geological record, or in other words, a place where rocks that may once have existed have been worn away, and new rocks have been laid down on top of the eroded surface millions of years later.) However the Arran locality is not so clear, and he continued the search, also finding an unconformity near Jedburgh.
Finally, having observed that some rocks inland of the Berwickshire coast were near-vertical, and others near-horizontal, he reasoned that there must be, somewhere along the coast, a place where both vertical and horizontal rocks would outcrop together, so he hired a boat and went looking for it. Siccar Point is where he found it.
The finding of rocks which had obviously started as sedimentary, then were tipped up on end, then eroded, then covered by later layers of sedimentary rock, coupled with his observations of the slow processes of erosion and sedimentation, enabled Hutton to formulate his 'Theory of the Earth', in which he postulated that the Earth is not static, but dynamic, with rocks being formed, deformed and eroded in a continuous and never-ending process over many millions of years. He expressed this as 'no vestige of a beginning, no prospect of an end'.
Naturally his ideas fell foul of the establishment of the day, especially the religious establishment, who accused him of atheism, although they seem to have stopped short of using the term blasphemy to condemn him.
Over time, of course, the scientific world came to accept Hutton's theory, and all modern geology incorporates his view of the world.
See also NT2772 : Hutton's Section and Link

Siccar Point is a Site of Special Scientific Interest, and a Geological Conservation Review site.
The Geological Conservation Review (GCR) is a database of geological reference sites in Great Britain. It is published by the Joint Nature Conservation Committee (JNCC) in the form of site reports collected in printed volumes covering different geological periods and topical areas such as fossils, minerals or geomorphology. The site reports are gradually put online in a searchable database Link
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James Hutton (3 June 1726 - 26 March 1797), pioneer of the science of geology, was one of the extraordinary men of science and learning who flourished in Edinburgh in the latter part of the 18th century, in a period called the Scottish Enlightenment.
He was born in Edinburgh, and after briefly studying law, and then medicine, achieving an MD degree in Holland in 1749, he took up farming. In 1768 he turned to scientific investigation.
There are several localities known as 'Hutton's Locality', where Hutton observed features in the rocks that were counter to the prevailing view of the time.
Geologically, the conventional wisdom was that all the rocks on Earth had precipitated out of sea water at the time of the Flood. The part played by igneous rocks was entirely unrecognised.
On Arthur's Seat in Edinburgh Hutton noted that the sedimentary strata had been deformed, and that the deformation resulted from molten rock being intruded into the pre-existing rocks. The evidence for that is that the deformed sediments had been baked, both above and below, by the heat of the magma as it forced its way through the sediments. Therefore Hutton could demonstrate that the magma post-dated the sandstone, and that it had been molten or semi-molten when it was intruded.
In Glen Tilt, Hutton observed pink crystalline rock interfingering with grey schists, again showing that the crystalline material must have been intruded in a molten state into pre-existing rocks, and hence that not all rocks were of the same age, or formed by precipitation from sea water.
The Irish archbishop James Ussher (1581-1656) had counted back the generations listed in the Book of Genesis and calculated the time and date of the Creation as 'the entrance of the night preceding the 23rd day of October... the year before Christ 4004'; that is, around 6 pm on 22 October 4004 BC, by the Julian calendar.
At Siccar Point, on the Isle of Arran, and at Jedburgh, Hutton observed rock layers at a sharp angle to overlying horizontal sedimentary strata. He deduced that the underlying layers must have been deformed and tilted, and that for this to take place meant that the process of rock formation must have been going on for an inconceivable length of time.
These ideas were totally revolutionary when Hutton published his findings in a series of papers under the title 'Theory of the Earth', presented to the Royal Society of Edinburgh in the 1780s. The basis of his theory was that all geological phenomena could be explained by observable processes, and that these processes had been operating since time immemorial and would continue operating in all time to come.
Although fiercely opposed by the churches and by the geological establishment, Hutton's theory, termed uniformitarianism, is now accepted as the fundamental principle of the scientific study of geology.