Introduction

This evening I am reporting on a geological feature known as Hutton’s Unconformity on the Isle of Arran.

Image of Hutton’s Unconformity

Information on Isle of Arran’s Geology

The Isle of Arran lies off the West coast of Scotland. This island is very popular with students of geology. This is because the island contains 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. The latter is manifested in Goatfell  at 2910 ft ( 873 m) and generally more rugged terrain The southern half is underlain by Permian, Triassic, Jurassic, Cretaceous and Tertiary sediments and lavas. 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. This occurred before the upper strata (sandstone) had been deposited on top. This feature at Arran influenced Hutton to devise his Uniformitarianism theory. This essentially proposed that the earth was very much older than believed at the time.

Students inspecting Hutton’s Unconformity on Arran,

Rocks at Hutton’s Unconformity

Raised Beach near Hutton’s Unconformity

More information for the Visitor

When in Edinburgh visitors may wish to visit Dynamic Earth which is located near the Scottish Parliament. This is a science centre which explores the history of the planet earth. Additionally, the publication Visitors’ Guide to Scotland has a sections focused on Scotland’s geology and the Isle of Arran. ISBN of the book is 978-1-9161332-0-4. This is also available via Kindle.