Geology

Durlston's Geology

Durlston's coast forms part of the Jurassic Coast World Heritage Site. The Jurassic Coast is England’s only natural World Heritage Site.

World Heritage status was granted because of the site's unique insight into the earth sciences as it clearly depicts a geological ‘walk through time’ spanning the Triassic, Jurassic and Cretaceous periods.

If you were to walk its length you could view 160,000,000  years of history from the 250 million year old Triassic deserts of Exmouth to the 90 million year old Cretaceous tropical seas of Old Harry Rocks.

Durlston's rocks were formed in the late Jurassic and Early Cretaceous periods and the site provides a unique record of life and habitats in the early Cretaceous. 

Overview

Durlston's coastline forms part of England’s only natural World Heritage Site, the Jurassic Coast. The site is named after the geology of the best-known geological period found within it; however the geology of the Jurassic Coast actually spans almost the entire Mesozoic era and includes exposures from the Triassic, Jurassic and Cretaceous periods.

The Jurassic Coast is England’s only natural World Heritage Site. Awarded its status by UNESCO in 2001, it is the only place in the world where ~160 million years of uninterrupted Mesozoic strata is exposed. The site starts at Exmouth, East Devon, where red Triassic sandstones dating back 250 million years ago are exposed. The youngest exposures, dating as far back as the late Cretaceous, can be seen 95 miles to the East near Studland, Dorset.

The rocks that make up the coastline at Durlston were laid down during the Late Jurassic and Early Cretaceous and offer a unique insight into what the world would have been like between 150-140 million years ago. The rocks which form the Country Park are primarily Limestone – sedimentary rocks which are formed from organic material. Since the deposition of these ancient sediments, tectonic activity has tilted the strata away from the horizontal to form the Purbeck Anticline, which can be viewed in Durlston Bay through 130m of exposure.

Schematic of Durlston from looking West

The Purbeck and Portland Limestones have been quarried here for many hundreds of years forming the landscape we see today. The rocks themselves carry heavy significance to the park as nearly all of the buildings and dry stone walls are constructed from them.

The sea cliffs of Durlston Bay, which can be viewed from Durlston Head, display the finest sections of Purbeck Limestone in Britain. The Purbeck Limestone is famous for its diversity of fossil fauna which includes bivalves, gastropods, sharks, crocodiles, turtles, mammals and of course, dinosaurs. These rocks are not only important for their fossils, but how they shape our present-day soils and habitats, such as the meadows and downland which are full of lime-loving plants such as the early spider orchid and the cliffs which host our seabird colonies.

DURLSTON BAY FROM DURLSTON HEAD

Erosion has shaped the Purbeck coastline, inland, rivers wash away the softer rocks leaving river valleys. The sea is the most active agent of erosion around Durlston where sea currents, tides and waves batter the sea cliffs. The hard limestones of the southern cliffs act as a barrier to the sea’s erosion. This part of the coastline is concordant, where beds of varying rock types run parallel to the coastline. The East side of the headland and the neighbouring bays are part of a discordant coastline, where bands of different rock types run perpendicular to the coast. The variation in erosion resistance has caused the formation of Durlston Head, Swanage Bay, Ballard Point and Studland Bay.

If you would like to find out more about the geology and fossils at Durlston you can READ MORE by clicking the buttons below. 

The characteristics of the rocks that form Durlston’s cliffs make them unstable and dangerous, especially after heavy rain, or prolonged dry weather. We would discourage anyone from visiting the beach at Durlston Bay unless they are with an expert. The interesting geology can be viewed from the Clifftop Trail and some of the best examples of the rocks and their fossils from both the Portland and Purbeck series can be seen at the Castle. Fossils of good quality are rarely found in Durlston Bay. Stick to designated footpaths at all times.