The district of Morvern is made up of a fascinating variety of rocks that cover a huge span of geological time. The oldest rocks tell a complex story of mountain-building events many hundreds of millions of years ago. The youngest rocks were created by spectacular volcanic eruptions, which took place about 60 million years ago. In between there are layers which contain fossils from the time of dinosaurs.
The six stopping points on this geotrail take you on a journey through these different times...
1. Strontian Granite – Clach-Ghràin Sròin an T-Sìthein
Take the road from the Corran Ferry towards Strontian. Turn left about 4km before reaching Strontian and take the A884 to Lochaline. Once you cross the Carnoch River you are on the Morvern peninsula.
Look out for several high rock faces marked by obvious long shot-holes on the left side of the road as you drive along Loch Sunart. After passing the junction with the Kingairloch road you will have a good view of Gleann Dubh (black glen) on your right. During the 18th century lead was mined in this glen.
2. Moine Metamorphic Rocks – Creagan Cruth-Atharraichte Mòine
The road then descends down towards Gleann Geal (white glen). Some distance down this glen you finally leave the granite behind and pass onto steeply inclined psammites (metamorphosed sandstones). Stop in one of these small passing places and have a closer look at some of the naturally weathered outcrops to see the layering in these rocks.
3. Triassic Sandstone – Clach Ghainmhich Traisig
Just after crossing the River Aline you'll see a remarkable structure called an ‘uncomformity’ in a cutting on the right-hand side of the road. Here flat-lying red coloured sandstone of Triassic age lies horizontally on top of steeply folded mica schist.
400m on, stop on the right hand side of the road and walk 200m along a forest track to see small exposures of gently dipping Jurassic limestones. on your uphill side. These rocks contain numerous fossil shells, including ‘devil’s toenails’. These are fossiled sea creatures from the Jurassic period, 200 - 145 million years ago.
4. Basalt Lavas – Làbha Mèinneir
Continue on for another 1.5 miles and you’ll see some exposures of dark basalt lava by the side of the road. There are also good views from here of the east side of Loch Aline - a characteristic terraced landscape created by the weathering of separate lava flows.
5. The Silica Sand Mine – Mèinne Ghainmhich Shileaga
Turn left into Lochaline village and follow signs for the Mull ferry. Park in the car park just beyond the jetty and walk northwards along the road towards the sand mine. Then follow the path along the seaward side of the crushing plant. The sandstone is quite crumbly and you should be able to see large stockpiles of white sand. This quartz sand was originally deposited in a shallow sea some 130 million years ago. The sandstone is overlain in the cliffs behind the mine by much darker basalt lava.
6. The Wishing Stone – A’Chlach Rùnachaidh
Return to the village and head west towards Drimnin for about 5 miles. Beyond Fiunary, on the right-hand side of the road you will see an obvious wall of rock with a hole through the end of it. This is the known as the Wishing Stone. This impressive wall is a natural feature called a dyke. It is formed when tension in the Earth’s crust causes a long fissure to open up. This fissure was filled by molten rock (magma), which cooled and cyrstallised to create the dyke. This probably happened about 60 million years ago, shortly after the eruption of the volcano on Mull. While the surrounding rock has worn away over time, the harder rock of the dyke has remained. Similar dykes from the Mull volcano extend all the way to Northumberland in the north of England!