Exmoor
Exmoor is a dissected plateau of Devonian sedimentary rock, rising to 517 metres (1,696 ft) at Dunkery Beacon. It extends into Devon but the majority of the area is in Somerset. Much of the area is a National Park. The landscape is one of rounded hills, with hogs-back cliffs at the coast due to geological movements. Because of high rainfall there are boggy areas and the part by the Chains is a Geological Conservation Review site recognised as being nationally important for its south-western lowland heath communities and for transitions from ancient semi-natural woodland through upland heath to blanket mire. The Chains provides palynological record of a mid to late Flandrian vegetation history on Exmoor. The pollen sequence in the peat is calibrated by radiocarbon dating. The Glenthorne area demonstrates the Trentishoe Formation of the Hangman Sandstone Group. The Hangman Sandstone represents the Middle Devonian sequence of North Devon and Somerset. These unusual freshwater deposits in the Hangman Grits, were mainly formed in desert conditions.
As this area of Britain was not subject to glaciation, the plateau remains as a remarkably old landform. Quartz and iron mineralisation can be detected in outcrops and subsoil. The underlying rocks are covered by moors are supported by wet, acid soil. The highest point on Exmoor is Dunkery Beacon; at 519 metres (1,703 ft) it is also the highest point in Somerset.
Exmoor has 55 kilometres (34 mi) of coastline, including the highest cliffs in England, which reach a height of 1,350 feet (411 m) at Culbone Hill. However, the crest of this coastal ridge of hills is more than 1.6 kilometres (1.0 mi) from the sea. If a cliff is defined as having a slope greater than 60 degrees, the highest cliff on mainland Britain is Great Hangman near Combe Martin at 318 metres (1,043 ft) high, with a cliff face of 214 metres (702 ft). Its sister cliff is the 218 metres (715 ft) Little Hangman, which marks the edge of Exmoor.
Exmoor's woodlands sometimes reach the shoreline, especially between Porlock and The Foreland, where they form the single longest stretch of coastal woodland in England and Wales. The Exmoor Coastal Heaths have been recognised as a Site of Special Scientific Interest due to the diversity of plant species present.
The high ground forms the catchment area for numerous rivers and streams. There are about 300 miles (483 km) of named rivers on Exmoor. The River Exe, from which Exmoor takes its name, rises at Exe Head near the village of Simonsbath, close to the Bristol Channel coast, but flows more or less directly due south, so that most of its length lies in Devon. The river and the Barle Valley are both designated as biological sites of Special Scientific Interest. Another tributary, the River Haddeo, flows from the Wimbleball Lake.
The action of streams has cut combes through the hills down to the sea, which are now wooded, although much of Exmoor is open heathland. There is an outlier of Exmoor at North Hill near Minehead. Iron working was formerly carried out, probably from the Roman period onward.
Because Exmoor was a royal forest, i.e. a hunting reserve, it was unpopulated in Medieval times. The first house on the moor was only built at Simonsbath in 1654. It was not until the 19th century that farms were built around the moor.
The Brendon Hills are to the east of Exmoor and are an outlier of it. They are separated from Exmoor by the valley of the River Avill. They have the same undulating landscape. The Brendons reach a height of 422 metres (1,385 ft) at Lype Hill. Iron ore mining was carried out from Roman times up to the early 20th century.
Read more about this topic: Geology Of Somerset