The county of Somerset is in South West England, bordered by the Bristol Channel and the counties of Bristol and Gloucestershire to the north, and Wiltshire to the east, Dorset to the south, and Devon to the west. The climate, influenced by its proximity to the Atlantic Ocean and the prevailing westerly winds, tends to be mild, damp and windy.
Somerset is predominantly a rural and agricultural county. The main upland areas are the Mendip Hills in the east and the Quantock Hills further west, the Blackdown Hills form the county's southern border, and Exmoor is on the western fringes. Between the Mendips and the Quantocks is the large area of flat, low-lying ground known as the Somerset Levels. The county's main rivers are the River Axe in the northeast, and the Rivers Brue and Parrett which flow northwestward through the levels into the Bristol Channel.
The landscape is largely determined by the underlying geology. The Carboniferous Limestone that forms the Mendips has been eroded to form gorges and caves. Exmoor is an extensive area of moorland and a National Park and the Somerset Levels contains wetland areas of international importance for birds. The Quantocks and the Blackdown Hills are Areas of Outstanding Natural Beauty, and the island of Steep Holm, in the Bristol Channel, is one of many Sites of Special Scientific Interest. The M5 motorway runs diagonally across the county, which is served by a network of trunk roads. Several railway lines provide services to other parts of the United Kingdom, and Bristol Airport is in the northeast. Some traditional industries have declined, but the area is popular with tourists and famed for its Cheddar cheese and cider.
Physical geography
Somerset is a rural county in southwest England with an area of . It is bounded on the north-west by the Bristol Channel, on the north by Bristol and Gloucestershire, on the east by Wiltshire, on the south-east by Dorset, and on the south west and west by Devon. The county divides into four main geological regions, spanning the Silurian, the Devonian and the Carboniferous to the Permian, that influence the landscape. The central area has broad, flat plains and there are several ranges of low hills.
Topography The main upland areas are the Mendip Hills in the northeast and the Quantock Hills further west. The Mendips run west to east between Frome and Weston-super-Mare, overlooking the Somerset Levels to the south and the Chew Valley and other tributaries of the River Avon to the north. They culminate in the promontory of Brean Down, only to crop up again in the Bristol Channel as the islands of Steep Holm and Flat Holm. Steep Holm is part of Somerset while Flat Holm is the most southerly point of Wales. The Mendips are composed of Carboniferous Limestone and water erosion has created gorges, dry valleys, screes, swallets and caves as well as various karst features.
The Quantocks extend northwards from the Vale of Taunton Deane, for about to the north-west, ending at Kilve and West Quantoxhead on the coast of the Bristol Channel. They form the western border of Sedgemoor and the Somerset Levels. The highest point is Wills Neck, at . The Quantocks consist of sedimentary rocks from the Devonian period, originally laid down under a shallow sea and slowly compressed into solid rock. The landscape consists of heathland with heather, gorse and bracken, ancient woodland and pasture land, with steep slopes and wooded combes.
The Blackdown Hills form the southerly border of the county with North Devon. They are composed of Upper Greensand and form a fairly level plateau with steep slopes with incised valleys to the north but more gentle slopes to the south. Their highest point is Staple Hill (). Exmoor is a large upland area straddling Somerset and North Devon, close to the Bristol Channel. It is composed from the Exmoor Group of sedimentary rocks and is overlain by moorland with wet, acid soil. The Exmoor coastline has rocky headlands, ravines, waterfalls and towering cliffs that are the highest sea cliffs on mainland Britain. Exmoor also contains the highest point in the county, Dunkery Beacon at .
Near the coast, halfway between the Quantocks and the Mendips, and lying parallel to them, is the low ridge of the Polden Hills. On either side is a coastal plain and wetlands area known as the Somerset Levels, an area of about , much of which is about above sea level. The northeasterly part of the Levels is drained by the Axe and Brue, and the southwesterly part by the Parrett and its main tributary, the Tone. This part of the Levels has traditionally been known as Sedgemoor, and to the east is Glastonbury Tor, an isolated hill projecting from the low-lying plain.
Water features
The north coast is gently shelving with low cliffs and long stretches of sandy beach, some sections of which, especially in the northwest, are muddy. The principal coastal feature is Bridgwater Bay, and the only important harbour is at the mouths of the Parrett. The main rivers in Somerset rise in the hills and flow northwards and westwards into the Bristol Channel; these are the Axe, Brue, Parrett and its tributaries, and Exe. The source of the River Axe is at Wookey Hole Caves in the Mendip Hills. It flows through a ravine and then west through the village of Wookey. It splits into two parts which subsequently recombine, and flows across the moors, through Lower Weare and to the south of Loxton. It passes between Uphill Cliff and Brean Down and reaches the sea at Weston Bay; it forms the northern boundary of the county.
The River Brue flows through the Somerset Levels to the east of the Polden Hills. It rises in hills near the southern border of the county, flows through Bruton, where it is joined by the River Pitt, and on through Baltonsborough. The lower reaches have been diverted into a channel that joins the Parrett at Burnham-on-Sea in Bridgwater Bay. There is a raised bog in the central Brue valley and the surrounding area is a mosaic of swamps, meres and alder woodland. The River Parrett rises in the hills around Chedington in Dorset and flows northwestwards past Aller, Somerset, and through the Somerset Levels to Bridgwater, after which it becomes an estuary with its mouth at Burnham-on-Sea. The river has a tidal bore, similar to that in the River Severn. The Somerset Levels are only a few feet above sea level and liable to flooding. They are drained by ditches and channels that drain into the Parrett including the King's Sedgemoor Drain, just south of the Polden Hills.
The River Tone rises in the Brendon Hills, and is dammed near its source to form the Clatworthy Reservoir. It flows roughly eastwards, through Taunton to join the River Parrett above Bridgwater. The River Exe rises on Exmoor in Somerset, about south of the Bristol Channel, but flows more or less directly south, so that most of its course lies in Devon and its mouth is on the south coast.
Hills
Urban areas
Somerset is largely rural and the two main centres of population, Bath and Weston-super-Mare, were transferred to the unitary authority districts of Bath and North East Somerset and North Somerset respectively, in 1996 but are still part of the ceremonial county. The Somerset Levels are liable to flooding and the only significant towns are Glastonbury and Street which occupy slightly elevated locations on the Polden Hills.
Other large towns are Wells, Taunton, the county town, Bridgwater, Yeovil and Frome. Wells is at the foot of the Mendip Hills and was built on the site of a Roman settlement. It became important as a trading centre. It has been described as England's smallest city because of Wells Cathedral. Taunton occupies an inland site on the banks of the River Tone and has been in existence since at least Saxon times. It is home to the United Kingdom Hydrographic Office and the regional headquarters of such organisations as Defra and the Charity Commission for England and Wales.
Bridgwater is at the mouth of the River Parrett, inland and the lowest crossing place above the estuary. It was mentioned in the Domesday Book and was once a major port and trading centre, and is still a mainly industrial town. Yeovil is in the middle of the Yeovil Scarplands, an upland area on the southern borders of the county. It was settled in prehistoric times and Yeovil is also mentioned in the Domesday Book. The town is a centre for the aviation and defence industries and a major employer is the helicopter manufacturer AgustaWestland. Frome, another ancient settlement, occupies a site at the foot of the Mendips overlooking the River Frome. The town was dependent on the woollen industry, but is now associated with metal-working and printing, and large numbers of residents commute to Bristol and Bath.
Geology
The oldest rocks are of Silurian age (443–419 million years ago). They make up a sequence of lavas, tuffs (volcanic ash), shales and mudstones in a narrow outcrop to the northeast of Shepton Mallet in the eastern Mendip Hills. Rocks from the Devonian (419–359 million years ago) are found across much of Exmoor, the Quantocks, and in the cores of the folded masses that form the Mendip Hills.
Carboniferous Period (359–299 million years ago) rocks are represented by the Carboniferous Limestone that forms the Mendip Hills, rising abruptly out of the flat landscape of the Somerset Levels. The limestones contain fossils of crinoids (sea-lilies), corals and brachiopods, providing evidence of the abundant marine life that existed in the shallow tropical seas that covered these areas at that time. Some hills, such as in the Mendips, are in excess of above sea level, and from them flow rivers of substantial erosive power. Examples of erosion may be seen at Cheddar Gorge and the caves within it, where the soft limestone has been scoured into gorges and caverns of great depth and length. At the end of the Permian (299–252 million years ago) and Triassic periods (252–201 million years ago), the Variscan orogeny resulted in the uprising of several mountainous areas including Dartmoor to the south, Exmoor, the Quantocks and the Mendips.
Much of the landscape falls into types determined by the underlying geology. These landscapes are the limestone karst and lias of the north, the central clay vales and wetlands, the oolites of the east and south, and the Devonian sandstone of the west. To the north-east of the Somerset Levels, the Mendips are moderately high limestone hills. The area of the central and western Mendip Hills was designated an Area of Outstanding Natural Beauty in 1972 and covers . The main habitat of these areas is calcareous grassland, with some arable agriculture. The Somerset Coalfield is part of a larger coalfield stretching into Gloucestershire. To the north of the Mendip hills is the Chew Valley and to the south, on the clay substrate, are broad valleys supporting dairy farming and rivers draining into the Somerset Levels.
Climate