Dartmoor. Dartmoor is an upland area in southern Devon, England. The moorland and surrounding land has been protected by National Park status since 1951. Dartmoor National Park covers 954 km 2. The granite which forms the uplands dates from the Carboniferous Period of geological history. The landscape consists of moorland capped with many exposed granite hilltops known as tors, providing habitats for Dartmoor wildlife. The highest point is High Willhays, 621 m above sea level. The entire area is rich in antiquities and archaeology. Dartmoor National Park is managed by the Dartmoor National Park Authority, whose 22 members are drawn from Devon County Council, local district councils and Government. Parts of Dartmoor have been used as military firing ranges for over 200 years. The public is granted extensive land access rights on Dartmoor and it is a popular tourist destination. Dartmoor includes the largest area of granite in Britain, with about 625 km 2 at the surface, though most of it is under superficial peat deposits. The granite was intruded at depth as a pluton into the surrounding sedimentary rocks during the Carboniferous period, probably about 309 million years ago. It is generally accepted that the present surface is not far below the original top of the pluton; evidence for this includes partly digested shale xenoliths, contamination of the granite and the existence of two patches of altered sedimentary rock on top of the granite.A considerable gravity anomaly is associated with the Dartmoor pluton as with other such plutons. Measurement of the anomaly has helped to determine the likely shape and extent of the rock mass at depth. Dartmoor is known for its tors-hills topped with outcrops of bedrock, which in granite country such as this are usually rounded boulder-like formations. More than 160 of the hills of Dartmoor have the word tor in their name but quite a number do not. However, this does not appear to relate to whether or not there is an outcrop of rock on their summit. The tors are the focus of an annual event known as the Ten Tors Challenge, when around 2400 people aged between 14 and 19 walk for distances of 56, 72 or 88 km between ten tors on many differing routes. The highest points on Dartmoor are on the northern moor: High Willhays, 621 m, and Yes Tor, 619 m, The highest points on the southern moor are Ryder's Hill, 515 m, Snowdon 495 m, and an unnamed point, 493 m at, between Langcombe Hill and Shell Top. The best-known tor on Dartmoor is Haytor, 457 m. For a more complete list see List of Dartmoor tors and hills. The high ground of Dartmoor forms the catchment area for many of Devon's rivers. As well as shaping the landscape, these have traditionally provided a source of power for moor industries such as tin mining and quarrying. The moor takes its name from the River Dart, which starts as the East Dart and West Dart and then becomes a single river at Dartmeet. It leaves the moor at Buckfastleigh, flowing through Totnes below where it opens up into a long ria, reaching the sea at Dartmouth. For a full list, expand the Rivers of Dartmoor navigational box at the bottom of this page. Much more rain falls on Dartmoor than in the surrounding lowlands. As much of the national park is covered in thick layers of peat, the rain is usually absorbed quickly and distributed slowly, so the moor is rarely dry. In areas where water accumulates, dangerous bogs or mires can result. Some of these, topped with bright green moss, are known to locals as feather beds or quakers, because they can shift beneath a person's feet. Quakers result from sphagnum moss growing over the water that accumulates in the hollows in the granite. The vegetation of the bogs depends on the type and location. Blanket bog, which forms on the highest land where the rainfall exceeds 2,000 millimetres a year, consists mainly of cotton-grass, sedges, Bog Asphodel and Common Tormentil, with Sphagnum thriving in the wettest patches. The valley bogs have lush growth of rushes, with sphagnum, cross-leaved heath, sundews and several other species.