Lulworth Cove and Durdle Door, Dorset

Discovering Geology — Maps and resources

This walk begins at Lulworth Cove on the coast of Dorset. The strata along the walking route consist of sedimentary rocks, with some spectacular folds seen along the walk. Both Lulworth Cove and Durdle Door are popular tourist destinations, so it is recommended that this walk is done in the early morning or outside of the tourist season.

A wide bay with yachts anchored and white cliffs
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Image A: Lulworth Cove. The Holywell Nodular Chalk Formation can be seen on the right of the image. The depression in the middle is the entrance to the cove. © Kotryna Savickaite.

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Geology and structure

The cove was formed when a weakness such as a fault or a crack within the Portland Stone Formation at the mouth of the cove was exploited by sea water. This allowed water to pass through and erode the softer rocks further inland. The result displays a beautiful array of sandstones, mudstones and limestones, all of which formed during the Cretaceous Period. The oldest rocks are at the mouth of the cove and consist of limestones of the Portland Stone Formation (152 million years old) and range through to the Holywell Nodular Chalk Formation (formed between 100 and 89 million years ago) at the back of the cove.

A cliff jutting out into the sea showing small arches at the base
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Image B: Stair Hole. Folding in the Portland Stone Formation limestone. © Cameron Fletcher.

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All the strata here form a part of the Purbeck Monocline, which reaches all the way to Isle of Wight. A monocline is a type of fold; the folding here formed 30 million years ago and is best showcased in the thin mudstone and sandstone beds around Lulworth Cove. The rocks of the Holywell Nodular Chalk are also folded and are nearly vertical here, but this is difficult to see because the formation is so thick.

Fossil forest

There are also some great fossils to keep an eye out for. In the thinner beds of sandstones, limestones and mudstones, for example, there are many ostracods, oysters and even some fish. There are also tufas, which are bowl-shaped fossils where trees used to be and rotted away, but the mould around its trunk fossilised. Fossils of trees themselves can also be found. Near these, you can also spot algal mats. However, Lulworth Cove is a Site of Special Scientific Interest and is also private land, so removal of any fossils is prohibited.

a circular, bowl-like depression in grey rock
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A tufa, or hollow fossil tree mould, at Lulworth Cove. BGS © UKRI.

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South West Coast Path

As you leave the cove and cross the car park to walk east towards Durdle Door along a path named Lulworth Steps, you will walk along the top of the Holywell Nodule Chalk Formation that forms the back of the cove. The path now forms part of the South West Coast Path, which stretches from Poole in Dorset around Cornwall to Exmoor in Devon.

Once you reach the top of Lulworth Steps, you get great views of the English Channel and, as you keep walking, you will come to St Oswald’s Bay and Man O’ War Cove. The bay is wide and has become a beach, whereas Man O’ War Cove still holds its distinctive cove shape. The rocks here are the same as in Lulworth Cove and this can clearly be seen in the folded sandstones and mudstones at the tip of the cove – they follow on directly from Lulworth!

A view from a clifftop across a curved bay with a beach at the base of steep cliffs
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Image C: Man O’ War Cove as seen from the South West Coast Path. The top of Durdle Door can be seen just behind the scree slope. © Cameron Fletcher.

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Durdle Door

Durdle Door is a limestone arch.  At its thickest at Durdle Door, the Portland Stone Formation is 33 m, but the arch top itself is just 5 m thick. If you decide to walk down to the gravel beach, you would be walking down some of the near-vertically dipping limestone beds, but the views are best from atop the path.  

A high rock arch over the sea with a beach at its base
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Durdle Door. © Kotryna Savickaite.

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If you were to extend your walk, you would no longer see the folded strata from Lulworth Cove or Durdle Door, only the large, rolling, chalk hills of the Dorset coast. Be careful, as they are uneven and steep — a good way to get your heart pumping!

Sandy beaches and white cliffs topped by grassland stretch into the distance
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The rolling chalk cliffs of Dorset to the west of Durdle Door. © Kotryna Savickaite.

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Flora and fauna

Along with the incredible geology, coastal Dorset is home to plants that only grow in coastal settings, such as the Portland spurge (found only in Dorset) or the slender thistle. It is also home to butterflies that are rare in the rest of country but common along the coast here, such as the Adonis blue and wall brown.

Map

Satellite image of the Dorset coast from Lulworth Cove on the right to Durdle Door on the left. Approximate locations of the images are labelled and the Lulworth Cove car park is shown by the yellow star.
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Satellite image of the Dorset coast from Lulworth Cove on the right to Durdle Door on the left. Approximate locations of the images are labelled and the Lulworth Cove car park is shown by the yellow star. Imagery © CNES/Airbus, Getmapping plc, Infoterra Ltd & Bluesky, Landsat/Copernicus, Maxar Technologies, Map data © 2022 Google Maps.

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Warnings

Do be careful when walking along the coast. Stick to the paths and keep away from the cliffs if you venture down to the water. These areas are known to have landslides and the sheer faces of the coastline can have rockfalls. Some people like to kayak under Durdle Door and other thin crevasses in the water, but do not attempt this because of the rockfall risk: remember, the erosion is still ongoing. Swimming around Durdle Door is extremely dangerous due to the swirling currents and waves.

Further information

About the author

Kotryna Savickaite is a geochemistry technician at the BGS headquarters in Keyworth, Nottinghamshire.

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