Hutton’s Unconformity, Isle of Arran, Scotland

This evening, I am focusing on the Isle of Arran, off the West coast of Scotland, which is very popular with students of geology owing to the island containing a diverse range of rock types and landforms concentrated in a relatively small area.

Arran forms part of the Tertiary volcanic region which extended from Northern Ireland to Iceland. The southern part features uplands rising to 1800 ft ( 550 m) while the north is much higher as manifested in Goatfell  at 2910 ft ( 873 m) and generally more rugged.The southern half is underlain by Permian, Triassic, Jurassic, Cretaceous and Tertiary sediments and lavas whilst the north is dominated by Tertiary granites surrounded by pre-Cambrian schists.

James Hutton ( 1726-1797) was a Scot who founded modern geology. He visited Arran in 1787. At a point near Lochranza Hutton noticed a rock strata inclined to the vertical which was overlain by another rock strata inclined to the horizontal. From this feature he concluded that the lower strata ( schist) had been tilted and eroded over a long period of time before the upper strata (sandstone) had been deposited on top. This feature at Arran influenced Hutton to devise his Uniformitarianism theory which essentially proposed that the earth was very much older than believed at the time.

Students inspecting Hutton’s Unconformity, Arran, Scotland

Rocks at Hutton’s Unconformity, Arran, Scotland

Raised Beach near Hutton’s Unconformity, Arran, Scotland