The Jurassic Coast
England's First Natural World Heritage Site
The Jurassic coast has been rated seventh on the list of 'must see' UK Tourist attractions. A survey of over 1,200 UK tourist ranked the World Heritage coastline as one of the most popular attractions alongside Alnwick Castle in Northumberland, the Royal Crescent in Bath and the Eden Project in Cornwall.
The Jurassic era started a little over 200 million years ago when sea levels rose to flood a desert landscape that existed during the Triassic Period. Throughout the Jurassic period tropical seas covered Dorset and marine life flourished. As sediments settled, the sea floor slowly subsided allowing many hundreds of metres of Jurassic sediments to accumulate. Subsidence and sea level change created deep water environments in which muds and shales settled and shallow seas in which sands and limestones accumulated.
The rocks of the Dorset coast generally dip gently to the east and this has the effect of exposing a complete sequence through the Jurassic period of geological time, from the oldest rocks around Lyme Regis to the youngest near Swanage.
The diversity of conditions and the sheer length of time in which these rocks formed are reflected in the great range of fossils to be found along the coast today. Towards the end of the Jurassic, sea levels dropped and land formed upon which the famous fossil forest grew. The forest can be seen in the Army Ranges at Lulworth and on the Isle of Portland. However, the forest was short lived as it soon became submerged by swamps and lagoons in which muds, sands and limestones formed. These sediments straddle the Jurassic/Cretaceous boundary at a time when dinosaurs ruled the land, leaving their footprints behind as fossilised trackways.
Later in the Cretaceous period, marine conditions again returned depositing first clays and sands and then a huge thickness of chalk. The Cretaceous rocks are very well developed along the Purbeck coast and are spectacularly exposed between White Nothe and Worbarrow Bay and from Durlston Bay, Swanage through to Old Harry Rocks. The pattern of rock types, thick bands of soft clays, massive beds of chalk and thin bands of hard limestone, have influenced the character of the coast. Folds and faults complicate the picture as they buckle and cut through the Jurassic and Cretaceous strata to form spectacular features such as the Lulworth Crumple.
For further information on the Jurassic Coast visit: Jurassic Coast