skip to main content

The Grampian Event of the Caledonian Orogeny

The first stage of the Caledonian Orogeny, the mountain-building event that brought the geological foundations of Scotland together, occurred 480-460 million years ago. In this period, a chain of volcanic islands, formed in the Iapetus Ocean, collided with the edge of the area we now know as the Grampian Highlands.

This is collision known as the Grampian Event. It created a range of high mountains and formed the Dalradian rocks from the sedimentary rocks which had accumulated at the edge of the ocean, through burial, heating and compression. The Dalradian rocks of the Grampian Highlands that we see today are the eroded roots of these ancient mountains.

Distinctive and varied rocks known as the Highland Border Complex are found along the line of the Highland Boundary Fault. These are believed to be partly the youngest parts of the Dalradian rock sequence, and partly pieces of ocean floor caught up in the collision of the Grampian Highlands and the volcanic island chain.

During and after the Grampian Event, molten rock formed and pushed its way into the deformed rocks of the Grampian Highlands. Much of this was granite which now forms distinctive mountain masses such as the Cairngorms, Lochnagar and Ben Nevis. At least some of this molten rock erupted as volcanoes at the surface. The most famous example is a caldera (or cauldron) volcano, the remains of which form the dramatic scenery of Glencoe.

Last updated on Wednesday 6th August 2014 at 14:24 PM. Click here to comment on this page