ROCK OF AGES

The geology of the far north-west of Scotland is a little

‘out there’ even by Scottish standards. It’s an area that escaped much of the main mountain-building episodes that shaped the Highlands, and is characterised by strange, isolated mountain bastions surrounded by miles of ‘cnocand-lochan’ moorland. The bedrock is Lewisian gneiss, one of the oldest known rock types in the world, dating back some 2.5 billion years. Some of the mountains in the far north-west are capped by light-coloured Cambrian quartzites, contrasting starkly with the red Torridonian sandstone underneath. Foinaven and Arkle in the far north of Sutherland are rare examples of mountains composed mostly of Cambrian quartzite, a relatively youthful type of rock at around 570 million years old. This lends these scree-clad peaks their ghostly pale appearance.