On island Arran, at the northern end near Lochranza.
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|Hutton visits Lochranza.
Ossian's Cave is a small sea cave at the northern end of the island Arran. It is a bit tricky to find, but markings of white colour are helpful. The cave is located at the foot of the cliff, above the beach. It is about three kilometers from Lochranza, along the right or eastern side of the cove. A single line road leads along the cove, and then up to about 30 m above sea level. At several single houses it ends, becoming a walking track, leading down to the beach. Here you turn right and follow the beach to the cave.
This is one of many Ossian's Caves, and probably the smallest and most uncomfortable one. Nevertheless, it is also the most interesting one, not because of the cave itself, but because of a first class geologic site nearby. This is the location of Hutton's Unconformity, which marks an interruption in sedimentation and also it marks a milestone in the history of geology. James Hutton (*1726-✝1797) visited Lochranza in 1787 and explored the coast to the north of the village. He noticed a simple fact: one rock strata inclined nearly vertically was overlain by another rock strata which was almost horizontal. The lower rocks were shist, the upper sandstone. He named it unconformity, as the two layers were not conform.
The main impact about this discovery, was his interpretation. He concluded that the layers of the lower rocks had been sedimented, then tilted and finally eroded. Later the upper strata was deposited on top of it. As it has not been tilted, it must be younger. Another result of this explanation is the enormous age of the earth. So he was the first to propose that the earth had developed over an immense period of time.
In one way this explanation marks the change between interpreting the bible to describe nature and interpreting natural processes to explain nature. Instead of supposing, that God made the rocks the way they are, he interpreted them as the result of erosion, deposition, and crust movement. Hutton formulated the Uniformitarian theory of geology, which suggested that geologic processes have been acting in the same manner and at the same rate over the whole of geological history.