Ben Nevis Geology
Ben Nevis consists mainly of igneous rock from the Devonian period (around 400 million years ago), intruded into the surrounding metamorphic schists during a period when Ben Nevis was part of an active and massive volcano; the intrusions take the form of a series of concentric ring dikes.
The innermost of these, known as the Inner Granite, constitutes the southern bulk of the mountain above Lochan Meall an t-Suidhe, and also the neighbouring ridge of Carn Mor Dearg; Meall an t-Suidhe forms part of the Outer Granite, which is redder in colour.
The summit dome itself, together with the steep northern cliffs, are composed of andesite and basaltic lavas. The mountain has been extensively shaped by glaciation and although the last ice age saw ice several kilometers deep it was not enough to cover the Ben Nevis summit.