Islay geology


Whisky on the Rocks, published by the British Geological Survey, claims that Bruichladdich’s whisky ‘milks the rocks of South America’.

Written by consultant geologists Stephen and Julia Cribb, the booklet explains the extraordinary geological journey of the rocks upon which Bruichladdich stands.

Bruichladdich is located on the oldest rocks of any distillery in Scotland – 1800 million year old Gneiss.

Whether looking at the map or standing on the shores of Lochindaal, it is clear that the far west of Islay, The Rhinns Peninsula, is different from the rest of Islay. When sea levels were higher, it would have been an island of its own.

The Islay geology is sperated by a feature known as the Gruinart Fault, along which a substantial earth movement occurred, which passes from Lochindaal through the narrow neck of low-lying land to Loch Gruinart.

Most of the rocks to the east of the fault, including Jura, were formed 800-600 million years ago (in the Dalradian part of the Precambrian period), folded into an anticline by the Caledonian Orogeny, causing the rocks to recrystalise, the process of metamorphosis.

These Dalradian rocks are old – but the Rhinns’ Gneisses, to the west of the fault, are even older at 1800 million years, making them the oldest in Scotland, bar Lewis.

These rocks are 3 times older than the rest of Islay. They are 4 times the age of the granite of the Speysiders Glenfiddich, Glenfarclas, Macallan etc., and 5 times older than the sandstones of Glenmorangie. They are 30 times older than the Volcanic Basalt of Talisker.

As Andrew Jefford says in his excellent book, Peat, Smoke and Spirit, ‘to put it in to perspective, the Bruichladdich Gneiss is 225,000 times older than the English Channel’.

Put another sobering way, imagine the history of the earth as a single day of the 24 hour clock: the Bruichladdich gneiss was formed at about 14.00, the dinosaurs appeared at 22.48 and were gone an hour later, and we humans arrived at 23.59 – and 52 seconds.

The Rhinns rocks fall into two categories: amphibolite gneiss and sedimentary sandstone. The former is hard, dark green and pink-banded, metamorphic rocks found in the southern part of the peninsula, and exposed on the beach in front of the distillery. The latter is grey-brown, hard sedimentary sandstones which occur in the lower, boggier ground in the north of the area.

The water we use for mashing, extracting the sugar from the barley grist, percolates through the peat of the low boggy hills behind the distillery, is collected in a shallow loch from where it is piped to the mash house; it is not influenced by the bedrock.

The water used at bottling, on the other hand, to reduce the alcohol level from cask to bottling strength, has percolated through the oldest rocks in the distilling industry. This emerges, clear, at Dirty Dottie’s spring in Gleann Mohr on the boundary between the sandstones and gneisses.

So where does this ancient gneiss rock of the Rhinns originate from? Surprisingly, it comes from South America. It’s hard to follow, and much is still theoretical, but thanks to Professor Ian Dalziel, it goes something like this:

750 million years ago (20.00 hours) the planet consisted of 3 great continents, forming one land mass called Rodinia:

Baltica (Europe)

Laurentia (North America & Greenland & North Scotland)

Gondwanaland (South America & Africa)

North Scotland formed part of the continent of Laurentia and South Scotland and England formed part of the continents of Avalonia and Baltica.

Professor Ian Dalziel believes that when Rondinia broke up around 600 million years ago, Laurentia moved apart from Gondwanaland, snapping the Rhinns of Islay off from Laurentia on to Gondwanaland (South America).

Between these two continents lay the Iapetus ocean. The continents then drifted back to each other, closing that ocean, forming Euramerica, then the large land mass of Pangea. The ocean floor of Gondawanaland was subducted, sinking underneath the overriding continental crust of Laurentia.

This Caledonian Orogeny, a mountain-building event, occurred 430 million years ago with the closure of the Iapetus Ocean, as the two continents collided together (again) with Baltica. This united England and South Scotland with North Scotland, and stuck the Rhinns on to Islay at Gruinart.

Subsequently with the break up of Pangea, around 150 million years ago, the continents again moved apart, but this time splitting along the present day west coast of Islay (from Portnahaven to Ardnave Point.)

And after complex plate tectonic pirouettes, the bit of land that was once home to the Rhinns, became the coast of Peru. Bruichladdich could have been located in the Pacific.

“The Rhinns’ gneisses have travelled for a 750 million years to provide an exotic whisky in terms of taste and geological romance; and their journey will continue for a thousand million more.”

Seismic activity continues to this day along the Gruinart fault line.

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