The Isle of Arran, located in the Firth of Clyde on Scotland’s south-west coast, is often called ‘Scotland in miniature’. Arran’s oldest rocks, in the north of the island, directly related to those in the Highlands of Scotland, are separated from younger rocks in the south by the Highland Boundary Fault. Hence the ‘Scotland in miniature’ moniker echoing the mainland’s Highland and Lowland topography and geology.
Arran is an undoubted jewel in the crown of Scottish Geology […] a superb outdoor geoscientific laboratory and educational centre. It is a truly unique world-class geological asset. Dr Colin CJ MacFadyen, Geologist, NatureScot
The Isle of Arran is unique internationally in its sheer geodiversity. Maarten Krabbendam, Chief Geologist Scotland, British Geological Survey
“One of the best locations for fieldwork in Europe” and nominated as one of the 100 Great Geosites “for its importance as a location for learning and understanding geology”. The Geological Society
Arran Bedrock Geology Map; for a more detailed maps, see the links below.Rocks that once were on the ocean floor between the areas we know as Scotland and England are testimony to the tectonic movements that brought together the foundations of the island. As part of the North Atlantic Igneous Province, some 50% of the island is igneous in origin. A large granite pluton, shot through by smaller dykes, makes up the core of the north of the island. Large sill intrusions at Drumadoon in the south-west and the dyke swarm at Kildonan in the south testify to continental crust being split apart with the opening of what is now the Atlantic Ocean.
While it is hard to pin down what makes a place special, there is no doubt that the nature of this much-loved island derives directly from its geological variety. It is an island with a strong identity which is loved and appreciated by the people who live there, and also by the visitors who come in great numbers, often for repeat visits. Prof Bob Holdsworth, FRSE, FGS
Arran Geopark is a wonderful opportunity for the people of Arran, Scotland and beyond, to nurture and enjoy all the natural riches of the island, encouraging the development of heritage, rural regeneration, and healthy living in the midst of the most extraordinary landscape, flora, fauna and biodiversity. Arran Geopark ensures a sustainable vibrant future for one of the world’s most beautiful islands.” Kirsty Wark, BBC television presenter and journalist
The Isle of Arran is the true Gem of the Clyde. Loved by the residents, and adored by visitors, it is truly a miniature Scotland. Billy Connolly, Scottish actor, musician, artist, and retired comedian
Dykes at Kildonan, looking towards Ailsa Craig.
The sheer variety of rock types and structures on Arran has for many years provided an excellent teaching ground used by students of Geology as part of their secondary education or degree-level studies. However, the stories of shifting continents and ancient environments and the cultural association with James Hutton, who used now-classic features of the island’s geology to help develop his Theory of the Earth, transcend academic research and teaching, and are there for all to explore and enjoy.
Nearly one third of Arran is designated as a Site of Special Scientific Interest for its geology. The island also contains 13 Geological Conservation Review sites.
Half of the island is a National Scenic Area, recognised as having outstanding scenic value of national importance.
For details of all of the island’s protected sites, please see our interactive map.
Further information
📍 Visit one of our interpretation centres, follow one of our geotrails, or join us on a guided walk!
📚 There are many books on Arran’s geology, here’s where to start
- Arran, Landscapes in Stone, written by Alan McKirdy, is a great book to begin to understand Arran’s landscape and its geology.
- Arran and the Clyde Island, A Landscape Fashioned by Geology, is a classic introduction to the area. FREE to download.
- The Geological Society of Glasgow provides detailed and informative excursion itineraries to three locations: Corrie Shore, Drumadoon, and Lochranza. All FREE to download.
- MacGregor’s Excursion Guide to the Geology of Arran is currently out of print, look out for secondhand copies, or download a FREE scanned copy.
- Exploring Geology on the Isle of Arran, by C. J. Nicholas. Part field guide, part workbook, it is designed with first-year undergraduates and A-level students in mind. Also out of print.
🗺️ Check out these amazing geological maps of the area
- The British Geological Survey’s (BGS) “Special Sheet” S21 & S13 provides the definitive record of the island’s “solid” i.e. bedrock geology.
- The BGS also has a free, interactive map covering all the UK’s geology.
- For super-detailed old geological maps, check out BGS’s historical map collection, which record the field mapping that contributed to the modern day geological map.
- Ready to go offshore? 🤿 Here are BGS’s Solid Geology and Seabed Sediment scanned high-res maps of the Clyde.
- The Scottish Geology Trust’s Geosites project is an amazing map-based viewer covering all of Scotland’s geology in great detail. It’s frequently updated by a keen group of volunteers and anyone can contribute.
🧭 Don’t visit Arran’s wild mountains and rugged coast without a good map
- The whole island fits on to one sheet of an OS Landranger 1:50,000 map, buy one here.
- For even more detail purchase an OS Explorer 1:25,000 map.
Using the Bookshop.org partner links above will help support local bookshops and Arran Geopark will be given 10% too.