Lulworth Cove was formed when the sea broke through the outer layer of hard Portland Stone to scoop out the softer Wealden deposits. At the end of the cretaceous period, 135 to 70 million years ago, violent earth movements, known as the "Alpine Storm" created the Alps, altered the sea levels and raised England as a land mass. These are the colossal forces which buckled and folded the Purbeck Stone strata like a sandwich to form the Lulworth Crumple.

Stair Hole is another Lulworth Cove in the making and eventually the two will merge and form an even larger cove.

The coastline from Lyme Regis to Swanage is of particular importance. Its rocks display 127 million years of the earths development. Every geology student is brought to this area since it provides the best exposure of rocks of their age in Western Europe.

Southampton University has carried out a number of geological surveys. These are documented for Lulworth Cove , Durdle Door and Stair Hole.

The oldest rocks visible in Dorset are at least 180 million years old. These are the blue grey bands of Liassic Limestone, which are exposed at low tide, as low slabs and rock ledges on the beach at Lyme Regis. These used to form the floor of the ancient seas which covered Dorset before the Jurassic period.

Towards the end of the Jurassic period there was a period of warm clear water in which coral flourished. This laid the beds of corallian rock which can be seen on the shore at Osmington Mills. So, the next time you walk to the Smugglers Inn, go down to the beach and take a look.

This was followed by an invasion of muddy water, which led to the formation of the Kimmeridge clay and bitumous shales. The thin laminated shale has been used to make bronze age ornaments and as fuel for cottagers fires. In more recent times the area has provided large quantities of high quality oil, which explains the "nodding donkey pump".

The raising of the land cut off the muddy waters and allowed the Portland beds to form in a clear shallow sea. Portland stone has been used in a number of famous London buildings, in particular, St Paul's Cathedral.

Eventually the shallow seas retreated leaving a pattern of freshwater lagoons. Deposits of freshwater snail shells led to the formation of the Purbeck Marble, which is a rich green colour when polished. This can be found between Worbarrow Tout and Peveril Point. The marble was used in medieval times by the early English church builders. Examples can be seen in Salisbury Cathedral and in the clustered pillars of Kingston Church near Corfe Castle.