Welcome to Islay and its wonderful variety of rocks. This website provides an introduction to the geology of the islands of Islay, Jura and Colonsay. It also includes links to events such as guided walks, and more information.

A geology guided tour of Islay
A guided geological tour of Islay

The Islay area is the best place in the British Isles to see the 1,800 million-year old metamorphic rocks (the Rhinns Complex) which underlie much of central Scotland.

Rhinns Complex gneiss at Lossit Bay

It has relatively undeformed sedimentary sequences (the Dalradian) deposited from 750-600 million years ago on the margins of the ancient Iapetus Ocean.

Folded metagreywackes near Saligo Bay

It has the world-famous Precambrian glacial deposit (the Port Askaig Tillite) that tells of a time of severe, perhaps global, glaciation.

The Port Askaig Tillite on the Sound of Islay

The island has the best evidence in the British Isles of Precambrian life in the form of fossil microbial colonies (stromatolites).

Stromatolites in the Bonahaven Dolomite near Bolsa

Islay has a variety of 60 million years old igneous intrusions related to the opening of the North Atlantic Ocean.

Cenozoic Dyke near Rhuvaal

and …. the islands have a wide variety of Ice Age erosional and depositional features

Post-glacial raised cliff-line with caves cut into an older raised late-glacial beach. Port an Chotain, North Islay
15,000 year-old glacio-marine gravels containing flint clasts at Kilchiaran Bay

Please follow these links to more pages or use the menu button



Islay Nature Centre

Islay’s geology

Geological summary


Current research





Past Events


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