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Dartmoor

National park in South West England

  • 23 min read
  • 11 chapters
View towards Sharpitor & Leather Tor down the valley of the river Meavy. The river Meavy is in the foregound. The forestry plantation is just above Burrator reservoir.
Myself - Herby talk thyme · CC BY-SA 4.0

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Through Sedimentary rock and Drainage basin

The granite that 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 wildlife. The highest point is High Willhays, 621 m (2,037 ft) above sea level. The entire area is rich in antiquities and archaeological artefacts.

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. The Dartmoor Commoners' Council exists to create and enforce regulations regarding commoners' rights.

Parts of Dartmoor have been used as military firing ranges for over 200 years. The public is granted extensive land access rights on Dartmoor (including restricted access to the firing ranges) and it is a popular tourist destination.

Physical geography

Geology

Dartmoor includes the largest area of granite in Britain, with about 625 km2 (241 mi2) at the surface, though most of it is under superficial peat deposits. The granite (or more specifically adamellite) 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.

Tors

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. Each tor represents a mass of granite left standing where deep chemical weathering removed the surrounding, more heavily jointed rock. 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 2,400 people aged between 14 and 19 walk for distances of 35, 45 or 55 mi (56, 72 or 89 km) between ten tors on many different routes.

The highest points on Dartmoor are on the northern moor: High Willhays, 621 m (2,037 ft), (grid reference SX 580892) and Yes Tor, 619 m (2,031 ft), (grid reference SX 581901). The highest points on the southern moor are Ryder's Hill, 515 m (1,690 ft), (grid reference SX 660690), Snowdon 495 m (1,624 ft), (grid reference SX 668684), and an unnamed point, 493 m (1,617 ft) at (grid reference SX 603645), between Langcombe Hill and Shell Top. The best-known tor on Dartmoor is Haytor (called Hey Tor by William Crossing), 457 m (1,499 ft), (grid reference SX 757771). For a more complete list see List of Dartmoor tors and hills.

Rivers

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. Other rivers flowing from Dartmoor include the Teign, the Taw, the Tavy, the Avon, and the Lyd.

Some of the rivers in Dartmoor have been dammed to create reservoirs for drinking water, including the River Avon and the South Teign River (Fernworthy Reservoir).

Bogs

Much more rain falls on Dartmoor than in the surrounding lowlands. As much of the national park is covered in thick layers of peat (decaying vegetation), 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 (or 'quake') 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 (79 in) a year, consists mainly of cotton-grass (eriophorum species), sedges (carex and rhynchospora), 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.

Some of the bogs on Dartmoor have achieved notoriety. Fox Tor Mires was supposedly the inspiration for Great Grimpen Mire in Conan Doyle's novel The Hound of the Baskervilles, although there is a waymarked footpath across it. Sabine Baring-Gould, in his Book of Dartmoor (1900) related the story of a man who was making his way through Aune Mire at the head of the River Avon when he came upon a top-hat brim down on the surface of the mire. He kicked it, whereupon a voice called out: "What be you a-doin' to my 'at?" The man replied, "Be there now a chap under'n?" "Ees, I reckon", was the reply, "and a hoss under me likewise".

The South West Peatland Project aims to restore around 300 hectares (740 acres) of Dartmoor's peatland through collaboration with the national park authority. Preserving these peatlands will help mitigate climate change through sequestering carbon from the atmosphere. More generally, Dartmoor aims to be carbon negative by 2045.

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