Islay Geology

Islay has had an extremely varied geological history reflecting the wide range of climates and environments that the Island has been subjected to over many millions of years. Whatever your experience or knowledge of geology there is plenty to see on Islay.

The Islay Natural History Trust Field Centre is a great place to learn about the geology of the Island. As well as a display, there are hands on activities (suitable for adults and children) and a library containing publications on, and associated with, Islay's geology. So if you are a beginner who is keen to learn more or an expert who wants to check out the latest research on the Island's rocks then visit the Field Centre at Port Charlotte.

NEW BOOK 2015 sees the publication of a new geological guide to Islay. Written by David Webster, Alasdair Skelton and Roger Anderton it describes 12 Excursions which explain the geology both for beginners and for those with some knowledge.

It can be purchased here: Geology of Islay Book

Some extra supporting information can be found on the companion pages Companion Site for Guide to the Geology of Islay Book


Why is the Geology of Islay so interesting?
Islay has a wonderful variety of accessible geology; virtually all aspects of the science can be demonstrated. Amongst the highlights are:
  • 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.
  • Relatively undeformed sedimentary sequences (the Dalradian) deposited from 750-600 million years ago on the margins of the ancient Iapetus Ocean.
  • The best evidence in the British Isles of Precambrian life in the form of fossil microbial colonies (stromatolites).
  • A world-famous Precambrian glacial deposit (the Port Askaig Tillite) that tells of a time of severe, perhaps global glaciation.
  • Relatively low-grade metamorphism resulting in the excellent preservation of the original depositional features of the sedimentary sequences.
  • Good examples of the re-activation and reversal of extensional faults.
  • A good place to study mineralisation and investigate fluid-flow in the Earth’s crust; at least three distinct episodes can be observed.
  • A variety of igneous intrusions related to the opening of the North Atlantic Ocean about 60 million years ago.
  • A wide variety of Ice Age erosional and depositional features
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A GEOLOGICAL MAP OF THE ISLAY AREA
Geological map Copyright: David Webster