The World Heritage Jurassic Coast line extends some 95 miles from Old Harry Rocks, Dorset to Orcombe Point , Exmouth in East Devon. The coast line displays Triassic, Jurassic and Cretaceous rock features representing almost the entire Mesozoic era.
The oldest rock forms, dating back some 250 million years, are found at the western end of the Jurassic Coast, to the youngest rocks being 65 million years old in the east end at Old Harry Rocks. This provides a 185 million year geological time period.
The Triassic Period is dated from 200 to 250 million years ago. At that time there were no continents as we know them today, only a vast super continent straddling the equator known as Pangaea. Britain was located in the centre of Pangaea, the climate was dry and arid with the landscape consisting of extensive desert basins. Red-coloured sandstone and mud were the main features of the landscape. Sediments consisting of desert sands and shallow lake mud stones accumulated in the large shallow basins. Huge rivers crossed the desert plains which were punctuated by mountainous areas formed by the older rocks of Dartmoor, the Mendips and the Malverns.
Forests of conifers and cycads, a tree resembling a palm tree were the major plant life replacing earlier plant forms, such as ferns. The first dinosaurs evolved and went on to dominate life during the Mesozoic Era. Most of our living groups of four legged animals had arrived by the end of the Triassic, including frogs, turtles and crocodiles. The first true mammals also evolved during the Triassic.By the end of the Triassic period and the beginning of the Jurassic Period the continental plates had started to drift apart, the sea-level started to rise, and a warm, shallow sea flooded over what is now Dorset and East Devon.
The Jurassic Period was 140 to 200 million years ago. Pangaea started to break apart during the Jurassic Period. The Atlantic Ocean opened to the west of Britain and the Americas drifted away from Europe. The extent of the oceans was far more widespread in the Jurassic then they had been in the Triassic period and warm shallow seas spread across Europe. Deeper waters occurred during times of fluctuating sea levels. There were hardly any ice polar caps. The climate was warm and moister than during the Triassic and the rock stratas of the Jurassic period are characterised by deep-water clays, sandstone and shallow water limestone. Seas were shallower in the Middle Jurassic, creating an environment of islands surrounded by shallow shoals, similar to the Caribbean of today. Seas then deepened again, and finally shallowed towards the end of the Jurassic, creating the conditions for a forest to flourish in a tropical swamp environment. These warm shallow seas were home to a rich diversity of life, Ichthyosaurs, Pliosaurs, Ammonites, and Belemnites. On the land enormous dinosaurs such as the Brachiosaurus and the Diplodocus evolved.
The Cretaceous Period, 65 to 140 million years ago saw much of the land masses covered by shallow continental oceans and inland seas. On what is now the south coast of England, the Jurassic Coast became first a gulf of salt lagoons covered with salt flats then lush swamps, before becoming a warm sea. Within the clear, warm waters billions of microscopic algae bloomed, and their skeletons sank to the sea floor to form the pure, white Chalk.
The Cretaceous is the time when some of the largest and most fearsome dinosaurs walked the Earth such as T-Rex, Velociraptor and Triceratops. It is also the period when the first flowering plants evolved. A mass extinction took place which brought to an end the reign of the dinosaurs, great marine reptiles and ammonites. The world that followed saw the present style of life on Earth emerge, dominated by mammals, flowering plants and grasses.
The Lulworth Coast stretches for 5 miles between White Nothe in the west to Worbarrow Bay in the east. The five types of rock at Lulworth (Portland, Purbeck, Greensand, Wealden and Chalk) are between 150 million years old and 65 million years old. The geology is important as it reveals the environment and creatures living at that time. The fossils within the rock are history set in stone.
Lulworth Cove is a pebble beach and by virtue of its natural protection is very sheltered. It was formed approximately 10,000 years ago by the awesome powers of a river and the sea. It continues to evolve behind a narrow Portland Stone entrance as the softer Purbeck, Wealden, Greensand and Chalk exposures are eroded. Lulworth is also home to the famous Fossil Forest where you can see the remains of growths that formed around tree stumps from about 135 million years ago.
Stair Hole is a cove that is forming just to the west of Lulworth Cove. The folded limestone strata known as the Lulworth Crumple are particularly visible at Stair Hole. This geological feature was formed at the end of the Cretaceous Period, where violent earth movements, known as the "Alpine Storm" created the Alps, altered the sea levels and raised England as a land mass. In a few hundred thousand years the cove may be as large as Lulworth Cove itself.
Further west along the coast will eventually take you to Man-o-War Bay and Durdle Door, a perfect coastal rock arch in the sea and one of the most photographed landmarks along the Jurassic Coast. Both beaches here are shingle.
The steps at the East end of Lulworth Cove beach lead to Fossil Forest and Mupe Bay with a stunning walk along the cliff top. The footpath is within the MoD Restricted Area and is only open at weekends and for the whole of August. Please check the information page as some weekends it is closed for firing.