Glacial Features

Most of the land forms that can be seen in Rannoch have been produced by the action of glaciers which last retreated about 10,000 years ago.

They include - Ribbon Lakes, Truncated Spurs, Roche Moutonnée, Striations, Kame deposits and Moraines.

Ribbon Lakes

These are formed when glaciers overdeepen valleys and the deepened sections flood after the ice has disappeared. Loch Rannoch and Loch Tummel are typical examples of Ribbon Lakes with the ice having flowed east from Rannoch Moor to Pitlochry.

Truncated Spurs

Truncated Spurs are formed when a glacier cuts off a ridge which is descending into a valley. Examples in Rannoch are Craig Varr and Drumglas. Here the steep rocks created have been cut and sculpted by glaciers flowing down the main valley.

Roche Moutonnée

Roche Moutonnées are formed when a glacier flows over a rock. As it does so it will scour the surface of the rock and creates low pressure on the lee side which then encourages freeze thaw action that plucks that side of the rock. The result is a characteristic shape which allows glaciologists to determine the direction of flow of the ice. The name Roche Moutonnée may derive from the resemblance of the rocks to a resting flock of sheep. Another possible derivation is that the rocks look like a judges wig which has been cast to the ground.

Striations

Striations are scratches created by ice flowing over the surface of rock. The glaciers carried a debris of stones and boulders which abraded the surface beneath and made deep scratches. The shape of the scratches shows the direction of flow of the ice because the scratches are deeper on the side from which the ice came.

Kame Deposits

Kame Deposits are heaps of debris left in a conical shape. They form as the ice melts and water flows down to the bottom of the glacier before dropping the debris which it carried. There is an example at the junction of the Over-Bohespic road near Trinafour.