Scottish Highlands - Geology

Geology

The Highlands lie to the north and west of the Highland Boundary Fault, which runs from Arran to Stonehaven. This part of Scotland is largely composed of ancient rocks from the Cambrian and Precambrian periods which were uplifted during the later Caledonian Orogeny. Smaller formations of Lewisian gneiss in the northwest are up to 3,000 million years old. The overlying rocks of the Torridonian sandstone form mountains in the Torridon Hills such as Liathach and Beinn Eighe in Wester Ross.

These foundations are interspersed with many igneous intrusions of a more recent age, the remnants of which have formed mountain massifs such as the Cairngorms and the Cuillin of Skye. A significant exception to the above are the fossil-bearing beds of Old Red Sandstones found principally along the Moray Firth coast and partially down the Highland Boundary Fault. The Jurassic beds found in isolated locations on Skye and Applecross reflect the complex underlying geology. They are the original source of much North Sea oil. The Great Glen is a transform fault which divides the Grampian Mountains to the southeast from the Northwest Highlands.

The entire region was covered by ice sheets during the Pleistocene ice ages, save perhaps for a few nunataks. The complex geomorphology includes incised valleys and lochs carved by the action of mountain streams and ice, and a topography of irregularly distributed mountains whose summits have similar heights above sea-level, but whose bases depend upon the amount of denudation to which the plateau has been subjected in various places.