COMPRISING ancient rocks from Cambrian and Precambrian times that were uplifted to form a mountain chain during the later Caledonian orogeny, the Highlands and Islands of Scotland lie to the north and west of the Highland Boundary Fault, which runs from Arran to Stonehaven. Indeed, Britain’s oldest rocks, among the oldest in the world—the 3,000 million-year-old Lewisian rocks—are found in the foundations of Scotland’s north-west seaboard. They form the basement to the west of the Moine Thrust on the mainland, in the Outer Hebrides and on the islands of Coll and Tiree.
The discovery of the Moine Thrust Belt in the 1880s, first mapped by
