Claim: The center part of the Dartmoor (one of the places where exposed masses of the Cornubian batholith granite rock can be seen) outcrop is a medium-grained granite with many very large megacrysts, while the main outcrop consist of coarse-grained megacrystic granite with small megacrysts.
Evidence: The granite which forms the uplands dates from the Carboniferous Period of geological history. The main exposed masses of granite are seen at Dartmoor, Bodmin Moor, St Austell, Carnmenellis, Land's End and the Isles of Scilly. The moorland and surrounding land has been protected by National Park status since 1951. The landscape consists of moorland capped with many exposed granite hilltops known as tors, providing habitats for Dartmoor wildlife. Dartmoor includes the largest area of granite in Britain, with about 625 km (241 sq mi) at the surface, though most of it is under superficial peat deposits. The geology of the national park consists of a 625 km (241 sq mi) core of granite intruded during the early Permian period into a sequence of sedimentary rocks originating in the Devonian and Carboniferous periods. For example, the Dartmoor granite was emplaced around 280 million years ago, with the cover rocks eroded away soon afterwards, exposing it to chemical and physical weathering processes. Dating of 28 tors on Dartmoor showed that most are surprisingly young, less than 100,000 years old, with none over 200,000 years old. From gravity and magnetic geophysical data, the batholith is interpreted to extend from about 8°W, more than 100 km southwest of the Isles of Scilly, to the eastern edge of Dartmoor.