The Ancient Rocks
Rocks are usually stacked on top of each other in the order in which they were formed, with the oldest at the bottom and the youngest at the top. The rocks of the Sleat Peninsula and adjoining areas of Skye, however, demonstrate that this is not always true. This area is on the north-western edge of what was the Caledonian Mountain Belt. During the formation of this mountain belt, the rocks were tightly folded and overturned so that now they can be right way up or upside down depending on where they are in the folds. On a larger scale, huge sheets of rock several hundred metres thick have been carried many kilometres towards the north-west, sliding over the top of one another so that in general they are now stacked with the oldest on the top. The gently sloping planes of sliding between the transported sheets are known as 'thrusts'. These can be distinguished by zones of very fine-grained rock formed by the intense grinding which took place as the rock masses were moved. The whole terrain affected by these thrusts runs throughout north-west Scotland from Iona in the south to Loch Eriboll in the north and is known as the 'Moine Thrust Zone'.