The Rocks Remain –
But Rarely Unmoved
The Moine Thrust
The Moine Thrust and the Moine series of rocks get their name from that well know barrier to communications in Dùthaich MhicAoidh – A’ Mhòine or The Moine. The Gaelic means peat or peaty place or a moss. Dwelly gives ‘ris a mhòine’ as ‘making peats’. Historically The Moine was a significant barrier to comunications between Tongue and Farr and Durness and Eddrachilles, much commented upon by Ministers of the past trying to tend to their parishioners across Mackay Country. It is for this reason that the construction of a road across the Moine in 1830 was considered of such importance. At the same time Moine House was built as a ‘refuge of the traveller’.[1]
The series of rocks known as the Moine Supergroup is made up of schists and psammite and were first studied and identified in The Moine area behind Melness. The Moine rocks dominate in Tongue and Farr and underly much of the Flow Country in Sutherland.
These rocks were also laid down as sediment in the Iapetus Ocean, in some places to an incredible depth of some sixteen kilometres. As Jim Johnson has noted that is ‘almost twice the height of Everest’.[2] As the Iapetus Ocean closed these sediments were put under unimaginable pressure – they were metamorphosed, folded and faulted. In addition to the Moine Thrust there are others in Tongue and Farr – most significantly the Kirtomy and the Naver Thrusts.
For 19th century geologists these thrust zones were a mystery. It was generally understood that younger rocks were to be found on top of older rocks. Before the days of plate tectonics the discovery of younger rocks underneath older rocks puzzled and perplexed geologists like Peach and Horne, who were in the area undertaking the Geological Survey for many years.
[1] From the plaque at Moine House commemorating the building of the road and the house by the Marquis of Stafford. The plaque was put up by James Loch Esquire MSP, Auditor and Commissioner upon his Lordships Estates.
[2] P29 J. A. Johnson 1997 Tongue and Farr 3rd Edition, Bettyhill
Another Fjord: Loch Erribol
Cambrian hills to the right of you, limestone outcrops to the left of you …...
View across the Kyle of Durness to the Parphe hills which are Torridonian sandstone on a bedrock of Lewissian gneiss. Beaches and dune system in foreground.
Geological Puzzles
In the early 20th century it gradually became clear that these ancient geological forces were such that several kilometres of older rocks were in places pushed across younger rocks. This was what happened in the case of the Moine Thrust. Once plate tectonics were understood, much later in the century, the discoveries made by Peach and Horne became widely accepted.
These thrust zones are geologically very complex and continue to fascinate geologists to this day. The Geological Survey began in 1884, a year after The Napier Commission began taking evidence from local crofters about the hardships created by ‘improvement’ and clearance. British Geological Survey geologists are currently remapping the north west, over one hundred year later.