The Rum Volcano
Most of the landscape of Rum was shaped by the formation of a volcano during the Palaeogene Period, some 60 million years ago. In the south of the island, the jagged peaks of the Rum Cuillin are obviously formed from rocks that are quite different from those that underlie the rounded hills to the west. However, all these different rocks represent the deeply eroded roots of the ancient volcano.
In the west, the more rounded hills such as Orval are composed of pale coloured granite, which has been worn smooth by the action of wind, water and ice. The more jagged peaks of the Rum Cuillin are composed of darker, rougher rocks called gabbros. In the next section, we will look at how these different rocks formed deep in the Earth's crust beneath the Rum volcano.