Most of Scotland is not granite, but volcanic and sedimentary in nature. The cairngorms are granite, but other areas are not. I would refer interested folks to two sources:

1. A Crack in the Edge of the World: America and the Great California Earthquake of 1906 (P.S.) by Simon Winchester. It has an excellent discussion about the North American plate and plate tectonics in general, including some remarkable facts about the relationship between Scotland and Montana (now I have made you curious).

2. The usual: Wikipedia http://en.wikipedia.org/wiki/Geology_of_Scotland