You may have heard that the Himalaya mountains were born out of the collision of tectonic plates a long time ago, causing the Indian Subcontinent to push into the Eurasian continent, and uplifting the Earth’s crust into what it is today. Something similar but of a more intimate scale can also be seen in Knockan Crag in Scotland. Here, you can literally touch rocks that go back to a billion years ago, far older than the Himalayas.

Located in the northwest region of the Scottish Highlands, the Knockan Crag National Natural Reserve offers a unique window into the Earth’s seismic activities between 420 and 450 million years ago, when rocks deep underground buckled, bent, fractured and heated – a process known as metamorphism. In the case of Knockan Crag, metamorphism resulted in older rocks being pushed up to sit on top of younger rocks, a phenomenon that intrigued geologists who are used to seeing the reverse pattern.

The mystery of Knockan Crag was finally resolved in the late 19th century, thanks to the work of two British scientists Ben Peach (1842-1929) and John Horne (1848-1930) who showed that the curious layering of older rocks on younger ones was the result of metamorphism that occurred in several stages up to about 450 million years ago during the formation of the Caledonian mountain range. Peach and Horne called this dramatic horizontal thrust, the ‘Moine Thrust.; Because of their discovery, we now know that the Earth beneath us can move vast distances not just vertically as with the Himalayas, but also horizontally.

Visiting Knockan Crag

The Northwest Highlands were, and still are, remote and difficult to access. Along a coastal strip some 200 kilometers (120 miles) long and 15–25 kilometers (10–15 miles) wide the terrain is austere with isolated mountains rising above barren lower ground where knolls of bare rock lie among lochans and peat bogs. This geological region runs from the Isle of Skye northward through Kyle of Lochalsh, Ullapool and Assynt to Cape Wrath and Loch Eriboll (see map). Assynt provides some of the best formations of rock and the finest scenery. It is here that you will find the oldest rocks in Britian and among the oldest on Earth. These are the Lewisian Gneiss. These metamorphic rocks, formed by intense heat and pressure deep within the Earth’s crust, are dated to around 3 billion years old, predating life on Earth and even the formation of continents.