James Hutton, who was born in June 1726, is considered to be the father of modern geology. Before his groundbreaking work, prevailing theories about the age of the Earth were more religious than scientific; he challenged biblical notions that the Earth was only a few thousand years old, instead arguing that for the nature of rock formations to be explained, our planet had to be far more ancient.
At Glen Tilt in the Cairngorm mountains Hutton found igneous granite penetrating metamorphic schists, in a way which indicated that the granite had been molten at the time. This showed that granite formed from the cooling of molten rock, not precipitation out of water as others at the time believed, and that the granite must be younger than the schists.
He went on to find a similar penetration of volcanic rock through sedimentary rock near the centre of Edinburgh, at Salisbury Crags: this is now known as Hutton's Section. In 1787 his travels brought him to the north coast of Arran. Here he found sedimentary rock layers tilted up vertically, and overlaid by other sediments of a different age and at a different angle.
The lower layers of rock, he concluded, must have been deposited eons before, then later upturned. In these unconformities between rock layers, Hutton saw evidence of vast expanses of time in earth's history. He found other examples elsewhere, notably Siccar Point, SE of Dunbar.
His observations and critical thinking led to his main ideas. The processes that shape the earth's rocks are slow, continuous and cyclical. Rocks are formed, lifted up, twisted, folded, worn away, deposited, and new rocks formed. The driving force is volcanism and the processes continue today. Because the cycle is slow, a lot of time is needed, and therefore the earth is much older than previously thought.
These ideas eventually formed the basis of modern geology and have since been added to and more understood through better dating techniques. Hutton's work was useful to Darwin who needed an old earth if his ideas on evolution were going to work. Indeed, Hutton proposed several years before Darwin the concept of 'survival of the fittest'.
To find the site, first go to Arran - ferry from Ardrossan to Brodick, then drive north to Lochranza, or catch one of the frequent buses. A small road runs across the golf course to Newton Point on the north side of the Loch. Park near the end, then walk along the coast for about a mile, it can be boggy. The specific site is near where a small stream comes down to the shore, although much can be seen along the way.
Newton Point is also interesting as a good example of a raised beach caused by the land rising after the weight of the ice sheets was removed at the end of the last ice age. You will also find glacial erratic boulders along the shore. Much of Arran is of geological interest and many groups visit to explore its delights. There is a field studies centre in Lochranza.
Visit Arran Museum for more info, or see: (visit link
Or Wikipedia: (visit link