Dartmoor is the largest expanse of unglaciated upland in Great Britain and the largest granite surface in England. It is exceptionally important for the study of these and related earth science features. There are 21 geological Sites of Special Scientific Interest (SSSIs) and approximately 35 Regionally Important Geological Sites (RIGS) on Dartmoor. The Biodiversity Action Plan includes geological targets in a Habitat Action Plan for Rocks (which includes tors, clitter slopes, quarries, caves, and mines). Read the Dartmoor Habitat Action Plan for Rocks (523Kb - PDF Help)
The geology of Dartmoor has had a major influence on Dartmoor’s relief, soils, vegetation, farming, many of its buildings and much of its industry. The main type of rock is granite which is an igneous rock that pushed up under the surface around 280 million years ago. The heat and pressure this created altered some of the surrounding rocks and soils and as the granite cooled, mineral ore veins of copper, tin, arsenic and lead formed. Some of the granite, through the process of kaolinisation, formed china clay. This clay, together with the granite itself and the metal ores have been extracted from Dartmoor for centuries.
As the overlying layer of rocks and soils eroded away, particularly in the higher places where it was nearer the surface, the granite became exposed and formed the distinctive tors you see across the moor. The contraction of the granite as it cooled, and the action of rain and frost after it became exposed, have helped create the cracks and fissures which are a distinctive feature of these tors.
The Dartmoor National Park Authority organised an exhibition called Dartmoor Rock in 2003 with English Nature and the Devon RIGS Group. This was visited by thousands of people and the material is now available online at Dartmoor Rock.
You can find out more about Dartmoor’s geology and landforms by reading:
Exploring a Dartmoor Valley-The Meldon beneath our feet.
Geology and Landform factsheets
The Evolution of a Dartmoor Landscape: Exploring Burrator ( PDF Help - 1000Kb) This publication is available for purchase from our on-line shop.
Detailed geological information about the Meldon area is available from our online Case Study.
There is also an Educational Register of Geological sites available from the Devon County Council website. (external link, opens new window)