Advent calendar

Door twenty

TwentyAn ancient Neolithic site, hewn from the UK’s oldest rocks, is behind door 20 of the #geoadvent…

The Neolithic stone circle of Callanish on the Isle of Lewis in the Outer Hebrides off Scotland was hewn from the UK’s oldest rocks, the Lewissian Gneiss.

At 3 billion years old, the rocks were formed during the Archaean period (3.5-2.5 billion years ago), and were squashed and heated by the pressure of continents colliding and separating, separating out their light and dark minerals.

Brent Bouwsema, whose images of Glencoe and the Callanish Stones feature in the 2016 100 Geosites calendar, also sent us this stunning image, showing the Stones beneath a dramatic sky.

Callanish Stones c Brent Bouwsema

Callanish Stones c Brent Bouwsema


The Callanish Stones were built around 5,000 years ago. Their purpose is uncertain, but it has been suggested that their positions are aligned to the movements of the moon. Some ancient legends suggest they are giants, petrified into stone for not converting to Christianity.

Daniel Hill sent us this beautiful black and white image of the Stones. He says,

‘The Outer Hebrides are a landscape photographers dream. The western coast of the Isle of Lewis is dotted with historical sites, but the Callanish stone circles give a unique perspective on the landscape. The beautiful patterns of the Lewisian Gneiss contrast with the complex coastline and the ever changing atmospheric conditions. It is also amazing to think that the view has been admired by people for thousands of years and yet the rocks themselves are billions of years old.

Callanish c Daniel Hill

Callanish c Daniel Hill


The first accurate geological description of the Callanish Stones was by John MacCulloch in 1819. MacCulloch was a well known Scottish geologist, who served as President of the Geological Society from 1816-1818, and produced the first complete geological map of Scotland in 1832, which was published posthumously in 1836.

Austin Taylor, whose image of The Snap, Funzie, features as the January image in our calendar, sent us this beautiful silhouette of the Stones.

Callanish Stones c. Austin Taylor

Callanish Stones c. Austin Taylor

There are still copies of the 100 Great Geosites 2016 calendar available to buy at Burlington House, or via our website – order while stocks last!

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