Wester Ross
The mountains are made of a very old Precambrian rock known as the Torridonian sandstone formation. It was laid down in the Mesoproterozoic and Neoproterozoic eras. It is just a small part of what was once a huge supercontinent. The remains of this are in parts of Scandinavia and North America. These rocks are of Archaean and Paleoproterozoic age, ranging from 3.0–1.7 billion years (Ga) ago.