Geology
The Cairngorms were formed 40 million years before the last ice age, when slight uplift raised an eroded peneplain based on an exposed granite pluton. The highest present-day peaks represent eroded monadnock hills. During the ice ages the ice caps that covered most of northern Scotland remained static, frozen to the ground for long periods and actually protected the rounded summits and valleys and deep weathered granite of the mountains of the area. Glacial erosion is represented in deep valleys which dissect the area. Many valleys are littered with glacial deposits from the period of glacial retreat. The most famous valley is the Lairig Ghru pass, a gouge through the centre of the mountains—a u-shaped valley, now partly filled with extensive scree produced by intense frost action during ice-free periods. Many parts of the Cairngorms exhibit classic periglacial weathering which occurred during cold periods in ice-free areas.
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