Brentor is an amazing location. A little church perched on the top of a tor. But it is even more special because unlike Dartmoor itself, which is an igneous intrusion, Brentor was a volcano in the sea producing basaltic lava flows on the surface. Basaltic lava in the sea produces what they call "pillow lavas" after the shape of the deposits but apparently that didn't happen here
http://www.devon.gov.uk/geo-brent-tor.pdf and
http://www.dartmoor.gov.uk/learningabout/lab-printableresources/lab-factsheetshome/lab-geologylandforms
