Take a trip to the beautiful beaches at Sanna Bay and travel through the roots of an ancient volcanic centre (volcanic centre 3), the last of the three volcanoes to erupt in the area in the early Tertiary.
The remains of this volcanic centre (centre 3) are best seen from a track heading towards the deserted village of Glendrian, approximately 1km south-east of Achnaha. However, details of all three volcanic centres and their origins can be found on the Lochaber Geopark Interpretation Board at Mingarry Pier.
Take the single track road B8007 towards Kilchoan on the Ardnamurchan peninsula. At Kilchoan, take the minor road to Mingarry Pier (as signposted) and stop off to examine the Lochaber Geopark board situated by the ferry terminal. The interpretation board shows location of each centre, the underlying geology and the different types of intrusions associated with the volcanic centres. Mingary Castle, which can be seen from the pier, sits on two such horizontal intrusions (sills), an granophyre sill and a dolerite sill, which overlay Jurassic metamorphic shales. Prominent dykes can also be seen along the foreshore where magma has intruded vertically into the Jurassic limestone.
On your return to the B8007, make time to stop off at the Community Centre at Kilchoan, where there is a geological map of the Ardnamurchan peninsula and some local rock samples.
Return to B8007 and once passed Kilchoan, take the minor road on the right hand side towards Achnaha and Sanna Bay. Continue along this road for about 4 km. Park at the old quarry car park approximately 1km south-east of Achnaha.
Head north along the gravelled track towards the deserted village of Glendrian. Climb to the crest of some nearby hills where you will be in a position to observe a nearly complete ring of small hills, the solidified remains of a subterranean magma chamber and its feeder pipe. This spectacular gabbro intrusion is known as The Great Eucrite of the Ardnamurchan Paleocene igneous complex. It is often described as a classic example of a ring-dike although, more recently, it has been suggested that the Great Eucrite ring-dike may be a lopolithic intrusion with a funnel-shape geometry.
Take time to admire this spectacle ring of Eucrite hills as you immerse yourself in the tumultuous geological history of Ardnamurchan peninsula.
From the viewpoint, you can either return to the car park or continue along a farm track to explore the deserted village of Glendrian, before returning by the same route.
You can also extend the walk to the beautiful shingle beach at Port Eigin-aig. This walk affords an opportunity to explore the Ben Hiant intrusion as well some sedimentary rocks. The small inlet also offers some fine views of the Small Isles. However, please note that the walk to Port Eigin-aig requires good navigation skills and should only be undertaken by suitably experienced and equipped walkers.
Details of both walks can be found on the Wild About Lochaber website.
From Achnaha, continue along the minor towards Sanna Bay, where there is an interpretation board at the far end of the car park produced by The Lochaber Geopark. The interpretation board provides some fascinating facts about the Great Eucrite ring complex that you have just visited at Achnaha. From the interpretation board you will discover that The Great Eucrite ring complex is one of three ring complexes evident on the Ardnamurchan peninsula; a map shows the position of all three Centres. The ring complexes were first described by J.E. Ritchie in 1920.
Whilst at Sanna Bay, take time to explore the beautiful sandy beaches, lapped by turquoise seas. Sanna Bay also provides an opportunity to study the gabbros formed from the second volcanic centre; these form the low lying headlands along the coast. In contrast, the highly resistant gabbros of the Great Eucrite form the hill, Meall Sanna, which lies to the south-east of the bay.