Purbeck Coast, Dorset World Heritage Area

The Purbeck Coast he youngest rocks in the Devon & Dorset World Heritage Site

• Weymouth to Ringstead. To the east of Weymouth the coast is made up of a complex sequence of rocks, which have been jumbled up by folds and faults. The cliffs are formed from Upper Jurassic clays, limestones and sandstones. The coast around Osmington is famous for a natural seep of oil from the seabed. The rocks once formed an oil reservoir that has been breached by erosion. On a calm day, oil can still be seen seeping onto the surface of the sea near Bran Point, between Osmington Mills and Ringstead. The coast around Osmington Mills is a good place to see trace fossils. These are the fossilised burrows made by ancient marine animals.

• Lulworth Cove. Lulworth Cove where a perfect horseshoe bay has developed where a stream cut through the limestone and let the sea enter the valley and hollow out the softer clays lying behind the limestone barrier. The Cove is one of the most famous features within the World Heritage Site. Another bay is forming beside Lulworth at Stair Hole, where the breach has been made by collapsing caves and arches. Half a mile west of Lulworth Cove is Durdle Door - a perfect coastal arch. The arch shows how nature creates landforms that are self-supporting. The Fossil Forest can be seen east of Lulworth Cove on a wide ledge in the cliff. The coast between Lulworth and Kimmeridge lies within a military firing range and access to the area is restricted. The range walks are open through most weekends of the year and during the school holidays.
• Kimmeridge. The rocks at Kimmeridge Bay were in the Jurassic period, 155 million years ago, on the bed of a deep, tropical sea. The sequence of rocks here an excellent record of this part of the Jurassic and geologists have adopted Kimmeridgian as the term for rocks of this age all around the world .Hammering is forbidden here and you may only collect loose fossils from the beach. BP's 'nodding donkey' has been producing oil since 1959. The oil formed in rocks on a stagnant sea floor. The rocks were buried and organic matter within them formed oil and gas.This is the Wytch Farm Oilfield, the largest onshore oil field in the UK.
• Durlston. Durlston Head has the Victorian Durlston Castle on top, with views of the English Channel, Durlston Bay and the Isle of Wight. Durlston Castle was part of George Burt's failed attempt to build a series of grand houses here in 1862.Massive limestone cliffs run east from St Aldhelm's Head. A geological fault has brought the Purbeck Limestones down to sea level, and the sea has created the landslipped coast of Durlston Bay in the softer rocks.
• Swanage. The World Heritage Site finishes just beyond the great Chalk headland of Ballard Down, and the stacks called 'Old Harry Rocks'. The Chalk downland here is owned by the National Trust. To the east, the Needles on the Isle of Wight are usually visible. These too are made of Chalk and only a few thousand years ago were connected to Ballard Down. At Old Harry Rocks were caused by the waves attacking weak joints in the chalk rock to form arches and caves, which then collapse leaving isolated stacks like 'Old Harry'

Purbeck-Portland Limestone. Quarried from Tilly Whim Caves, Dancing Ledge and Winspit the Purbeck-Portland Limestone provided the building stone for houses such as, Lulworth Castle, And Durlston Castle. It was also shipped to London. Galleries were driven deep into the cliffs and the blocks of stone were loaded on barges using cliff-mounted cranes. Today the galleries are both derelict and dangerous. Two Purbeck quarries working Portland Limestone are still open today, St Aldhelm's Quarry which provides a polished limestone known as Spangle and the much larger Swanworth Quarry where the Portland Limestone is quarried for aggregate.

The Purbeck Stone. Within the clays and limestones that make up the Purbeck Beds, several feature as a source of stone, with names like Roach, Thornback and Grub, each with their own qualities. These rocks were once worked underground around Acton, Townsend (in Swanage) and along the coastal slopes around Durlston. Today the stone is worked in open cast sites around Acton.

Devon and Dorset World Heritage Coast