136 - South Purbeck : Description

Physical and functional links to other National Character Areas

A part of the Purbeck Monocline, the steeply dipping chalk buttress of the Purbeck Ridge dominates, shelters and delineates much of the National Character Area (NCA), while also continuing, across the English Channel via the Old Harry sea stacks, to The Needles and the Isle of Wight. The gently seaward- dipping limestone plateau can be seen, continuing on the Isle of Portland.

The gap in the ridge at Corfe Castle provides the principal transport link into the NCA, allowing passage for the railway and the A351 which both run between Wareham and Swanage. The Corfe River also flows northwards through this gap into Poole Harbour.

From the ridge northwards, long views are afforded over heathland, plantation and the wetlands of Poole Harbour and the valleys of the Frome and Piddle in Dorset Heaths NCA. Beyond this rise the chalk downs of Dorset Downs and Cranborne Chase NCA.

The coastal strip with its maritime cliff habitats provides a strong ecological link to the adjacent NCAs including Weymouth Lowlands to the west and Dorset Heathlands to the east. The Dorset and East Devon Coast World Heritage Site (Jurassic Coast) and the South West Coast Path are strong cultural, recreational and processional links between coastal NCAs, principally to the west.

Long views along the coast and out to sea (including views of the Isles of Portland and Wight) provide a strong visual tie across and between NCAs.

Relatively unimpeded coastal processes also link this and adjacent NCAs via long shore drift and sediment cells. Offshore, the submarine geodiversity and seabed morphology are as varied as on the land. Terrestrial biodiversity is mirrored by an equally diverse suite of reef communities.

Distinct areas

• Chaldon Down

The South Purbeck today

South Purbeck is a landscape of contrasts. A vertiginous, exposed chalk ridge and wind-swept limestone plateau, a sheltered, gently undulating and often intimate central valley, rolling downland and a rugged, dynamic coast bear witness to and often reveal the underlying strata. This geological and geomorphological diversity is bound by a strong unifying cultural identity, drawing heavily on this area’s past.

The whole NCA is predominantly rural and agricultural in nature. Livestock grazing, principally cattle and sheep, predominates. The pattern of hedges and fields in the Corfe Valley becomes smaller and more irregular to the north and west where small farmsteads are hidden in an intricate network of lanes. To the south and east, the fields are larger, extending up the slopes of the limestone plateau. The area around Chaldon Down presents further contrast. Here, large rectilinear arable fields mark well-drained, fertile soils lying over chalk.

The NCA is not well wooded, but trees and small woodlands are important. Clinging to the sheltered northern edge of the Purbeck Ridge, ancient semi-natural beech and oak woodland is found, a key habitat for Bechstein’s bat. These, along with three principally conifer plantations, are the only woodlands of significance. The limestone plateau and top of the Purbeck Ridge are mainly treeless, a combination of exposure and thin soils stunting growth. Small ash and sycamore woodlands thrive in the most sheltered sections of the coastal valleys.

Patches of scrub and scrappy hedgerows do provide important ‘wooded’ features and important refuges for birds and other animals. In the central valley and other sheltered areas thick hedges, shelter belts and small copses enclose fields and hamlets alike and create a sheltered, intimate landscape. The top and southern slopes of the Purbeck Ridge used to be almost exclusively open grassland but in recent decades scrub, mainly gorse, has gained an increasing hold on the slopes.

Limestone and chalk high ground quickly absorbs precipitation into the well-drained strata. There are no surface waters here and even ponds are few. However, as the water meets impermeable strata, springs and flushed areas abound. In the central valley these feed networks of small streams that empty into the sea at Swanage, via the Swan Brook and, as the Corfe River, out of the NCA through the impressive gap in the Purbeck Ridge at Corfe Castle. The small streams and flushes support stands of alder trees and in places fen and wet meadow habitats. On Corfe Common the flushes and runnels are home to the rare southern damselfly. On the coast, the spring line is well below the tops of now dry valleys incising the plateau.

The well-drained and fertile limestone plateau comprises rectilinear fields of arable and semi-improved grazing, protected from the wind by a network of stone walls. A concentration of arable fields around St Aldhelm’s Head hosts a relict population of corn bunting, a rare farmland bird. Other farmland bird species including linnet and skylark are more widespread. Arable plants such as corn gromwell, corn parsley and shepherd’s needle are also found in nationally significant numbers. The exposed coast features large areas of unimproved grassland which is mainly calcareous in nature; similarly, the Purbeck Ridge features calcareous grassland and areas of unimproved and semi-improved acid grassland. Much of this was, until the middle of the 20th century, an intrinsic part of the area’s agricultural system but it is now marginalised and suffers, in places, from a lack of necessary management – principally a lack of suitable grazing.

The area around Kimmeridge is exposed but fertile and features extensive improved and semi-improved grazing and some arable. The central valley is the most fertile and sheltered area, and clay and loam soils derived from underlying shales and alluvium from streams and the river support rich pasture. In places such as Corfe Common, fertility is low and soils are thin and waterlogged, giving rise to important semi-natural habitats such as fen and fen meadow.

The principal settlements of the NCA, Corfe Castle, Harman’s Cross and Swanage, are located along the main A351, running eastwards from the Corfe Gap. Swanage is a bustling seaside resort with many Victorian buildings and a typical collection of 20th-century resort vernacular styles. At its fringes caravan and camp sites (often in sites of old quarries) have developed. Corfe Castle is the ‘gateway’ to the NCA, featuring the imposing castle and picturesque stone-built village.

Off of the main road, winding lanes link small villages such as Langton Matravers and Worth Matravers and a series of hamlets and isolated farmsteads. Many of the buildings are of Purbeck Stone and Portland Stone. On the plateau, the small stone villages centred on the quarries are uniform in character. These settlements are busy in summer but, owing to the numbers of second homes and holiday lets, can be very quiet in winter. As one travels further west the villages and hamlets become smaller, within a much more enclosed landscape. Corfe Castle aside, there are few manor houses or major historic buildings, with the notable exception of Lulworth Castle.

South Purbeck’s character is strongly influenced by features from the past. The Purbeck Ridge is dotted with bronze-age barrows and at its far western end there is a hill fort. Traces of field systems, abandoned villages (often with a single farm remaining), tracks and quarries are frequent. Small quarries in particular pepper the limestone plateau, some now grassy depressions, others still nominally in production, surrounded by piles of stone.

Apart from agriculture and some limited operational quarrying, tourism visits are the major economic driver and force for change in South Purbeck. The coast provides the greatest draw. From the Chalk cliffs high above Swanage Bay, a complex and dramatic coastline sweeps round to Worbarrow Bay. Sheer white chalk and limestone cliffs contrast with sheltered coves at Chapman’s Pool and Lulworth Cove, and extend seaward as the Chalk stacks of Old Harry Rocks. To the west are the unstable cliffs at Kimmeridge. A near continuous strip of unimproved coastal grasslands features botanical highlights such as the early spider orchid and early gentian.

High wave energy and varied coastal geology have resulted in various erosional landforms. Many are typified by a breakdown of the resistant Portland strata, often by ancient (10,000 BP) fluvial processes, followed by rapid erosion of weaker Purbeck and Wealden Beds as sea levels rose and finally slower erosion of the chalk to form impressive cliffs, up to 170 m tall. The series of headlands and bays intercept littoral sediment drift, leading to between 8 and 11 discrete coastal sediment cells being identified. Only a small part of the coastline is defended outside of Swanage. Offshore sediment transport is constrained by a series of reefs and shelves and it probably cycles back landward into beaches.

The coast and Purbeck Ridge host much of the important habitat in this NCA. Calcareous grassland, acid grassland and coastal cliffs form much of the 1,415 ha (12 per cent of the NCA) of principally coastal habitats, designated as a Special Area of Conservation (SAC). Elsewhere, quarries, fen meadows, flushes, arable farmland, neutral grassland, ancient woodland and parkland all contribute to a diversity of habitats made possible by the underlying geodiversity. In fact South Purbeck falls within the 10 km square with the greatest plant diversity in the UK.

The largely unspoilt natural beauty of this NCA has been recognised by its designation as part of the Dorset Area of Outstanding Natural Beauty (AONB) (1959) and selection as a Heritage Coast (1970). The biological importance of the coast is recognised, at a European scale, through selection of most of the coastal part of the NCA as a SAC. In 2001 the 153 km of coast from Exmouth to Studland Bay were inscribed by UNESCO as a World Heritage Site, popularly known as the Jurassic Coast, in recognition of this coastline’s 185-million-year geological record, outstanding fossil record and geomorphological processes. All 42 km of the NCA coast are inside the World Heritage Site and all are part of the South West Coast Path National Trail.

The landscape through time

The rock record in South Purbeck extends from the Kimmeridge Clay of late Jurassic age through to the earliest deposits from the Eocene. Fluctuating sea levels and several phases of tectonic activity are evident.

The Kimmeridge Clay was laid down during a time of higher sea level and contains high levels of organic carbon. It is an important source of hydrocarbons in the North Sea and is studied on the Dorset coast.

Falling but fluctuating sea levels created shallow seas suitable for a highly fossiliferous limestone, Portland Stone, to form. The fluctuating environments, cycling between marine and freshwater (a conifer forest grew in marshy conditions at one time) at this point, gave rise to the different qualities and types of stone, the highly varied Purbeck Beds, which were to become desirable as building materials.

Following uplift in distant areas to the west and north, large rivers carried sand, grit and clay into the area, creating the Wealden Beds. A slow return to marine conditions began with the Lower Greensand but was interrupted by significant uplift and erosion across the region.

After sea levels rose and flooded this surface the Gault Clay and Upper Greensand were laid down. Sea levels continued to rise and the erosion that had previously supplied sediment to this area ceased, allowing the formation of the pure limestone called the Chalk. Following the end of the Cretaceous (65 million years ago) the chalk sea bed was uplifted and exposed to erosion here by the ongoing opening of the Atlantic Ocean. Deposition did not resume until the Eocene with a return to marine conditions. These deposits only appear north of the Chalk ridge and only the oldest of these rocks are included in the South Purbeck area.

At about 20 to 25 million years ago tectonic compression related to the closing of the Tethys Ocean as the African and European plates collided (creating the modern Mediterranean Sea and the uplifting of the European Alps) formed a structure known as the Purbeck Monocline. The key characteristic of this structure is the steep northern dip that it imprinted across the geological sequence here. As subsequent erosion cut into the monocline the variety of rocks responded differently, creating the area’s distinct geomorphology.

There is evidence of human activity in South Purbeck from at least the Mesolithic era, when the clay vale appears to have been intensively farmed and settled. The surrounding high ground most probably held considerable ceremonial value and has many neolithic, bronze-age and iron-age sites and barrows culturally linked with the South Dorset Ridgeway to the east.

Kimmeridge Shale was being used for ornaments in the Iron Age, when occupation of the valley was quite dense. By the time of Roman occupation this was a largely cleared and settled landscape with several villa complexes and continued shale working, an industry that continued into the Romano-British period (in relation to which over 50 sites are known).

Portland Stone and Purbeck Marble were quarried by the Romans and were also used in 11th- and 12th-century buildings. However, more rapid development of the industry began in the 13th and 14th centuries, the quarrying and carving developing as a major medieval industry providing monumental masonry for churches, cathedrals and public buildings. The Purbeck Stone quarries around Swanage were the most intensively worked, operating between 1700 and 1905, and leaving extensive abandoned workings. Today, the surface of the limestone plateau is pock-marked by hundreds of abandoned small quarries with more recent ones near the coast or actually into the cliff faces.

Shale, clay, alum and, most recently, oil have been extracted from the Kimmeridge Shale and, in the 19th century, there was a short-lived oil-shale industry manufacturing a wide range of products from the jet-like bituminous shale.

While the extractive industries developed and declined, the settlement pattern became one of a quite densely populated valley, a largely uninhabited Chalk ridge and quarrying settlements on the limestone. The ridge provided extensive common grazing.

Corfe Castle, started in the 11th century, has been a landmark ever since. It was one of the first stone castles in England. Various modifications and extensions over the centuries meant that the Roundheads could not assail it in the English Civil War. It was finally defeated through treachery and subsequently demolished with explosives, creating today’s impressive ruins.

During the Second World War, the village of Tyneham and surrounding land were evacuated to allow military training. The area was never repopulated and remains an area of intensive military use.

Despite the quarrying industry, the area has remained substantially rural even after the arrival of the railway and the development of Swanage as a resort. Visitors have always come to experience Corfe Castle and its village (approximately 190,000 in 2010), Swanage’s attractions and the spectacular 42 km of coastal scenery. The west of the NCA around Chaldon and the plateau, aside from Worth Matravers, are still much less frequently visited, although in high season they can become very busy.