geology

The Dartmoor granite was formed at the end of the Carboniferous period of earth history, but the whole story of how the granite came into being starts much earlier in the Devonian period and ends in the present day.
Its creation is intimately tied in to the surrounding geology of Devon, Cornwall and indeed Dorset, for those rocks also tell a story of crustal evolution. By studying the relationships of the different rocks, how they were formed and the fossil evidence within them, geologists can begin to build up a picture of what the world was like millions of years ago.

The Dartmoor granite is the largest of six granite regions and three smaller outcrops, which form the spine of the Southwest peninsula. It is the surface expression of a much larger mass hidden underground by the surrounding rocks. Although the granites of the south west vary in chemistry, crystal size and in the ages given to them by radiometric dating techniques, they are thought to be part of a much larger granitic mass underlying the region.

1	Isles of Scilly	290-285 Ma
2	Land’s End	280-275 Ma
3	Carnmenellis	295-290 Ma
4	St Austell	285-270 Ma
5	Bodmin Moor	290 Ma
6	Dartmoor	300-280 Ma

The granite regions and their age, (Bristow 1996)

This is known as a batholith. This linear feature is characteristic of other parts of the world and has been interpreted as a late stage in the development of mountain chains associated with continent collision. As the crustal plates of the earth move, very slowly over millions of years, they collide with each other. The result, earthquakes, volcanoes and mountain chains!