The county of Dorset, on the south coast of England, has one of the most fascinating coasts of any county, with many features of interest packed into a short distance. Here are some of Dorset’s natural wonders along this stretch of the world-famous Jurassic Coast.
Chesil Beach
This is a shingle ridge that connects the massive lump of limestone known as Portland to the rest of Dorset. It stretches for a total of 18 miles (29 kms), is up to 60 feet (18 metres) high and has created a salt-water lagoon, known as The Fleet, between itself and the mainland. At the far western end of The Fleet is the famous Abbotsbury Swannery.
A strange feature of Chesil Beach is that the pebbles that comprise it are graded in size, from “duck eggs” at the eastern end to “marrowfat peas” at the western end. Experiments have been done that demonstrate the process by which this happens – marked large pebbles will eventually be transported by the sea from west to east by the process of “longshore drift”.
The material that comprises Chesil Beach may have originated in landslides at the end of the last Ice Age, after which the sea gradually pushed the eroded material onshore. Chesil Beach has probably been in its present position about four or five thousand years.
Lulworth Cove
This is a small natural harbour that was created thousands of years ago when the sea broke through a narrow band of limestone rock and eroded the softer clays behind it, before being restricted by harder chalk rocks that now form a cliff at the back of the Cove. This is therefore a microcosm of the geology of much of southern England, with the broad swathes of Jurassic limestone (such as the Cotswolds) and Cretaceous chalk (such as Salisbury Plain), separated by broad clay vales, being reduced to a compass of a few hundred metres at this point.
Next door to Lulworth Cove is Stair Hole, which is a more recent example of erosion of the limestone. Eventually, Stair Hole and Lulworth Cove will join together. Stair Hole also shows evidence of ancient folding of the limestone in a dramatic “zigzag” of the strata at the back of the Hole. This is known as the “Lulworth Crumple”.
Lulworth Cove is a popular stopping-off point for sailors of small boats as they proceed up the Channel coast, as it offers a safe and sheltered anchorage.
Under the cliffs just to the west of Lulworth Cove a “fossil forest” can be seen. These are the fossilised remains of ancient tree stumps that were growing some 150 million years ago.
Durdle Dor (or Door)
A mile or so west of Lulworth Cove is another example of the power of the sea in eroding ancient rocks. The narrow band of limestone that once stretched along the whole coastline juts across a small bay, and a large hole has been cut through this outcrop to form a perfect example of a sea arch.
In calm weather it is possible to swim or canoe through the arch, or it can be admired from the shingle beach nearby, especially when the evening sun catches the Dor’s inner walls.
The name Durdle comes from Old English “thirl”, which means “to pierce”, and “pierced door” sounds like a perfect description.
Old Harry Rocks
These mark the eastern end of the Jurassic Coast, although the rocks are composed entirely of younger Cretaceous sediments.
The series of rocks that jut out into the sea from the end of Ballard Down are sea stacks that are entirely due to coastal erosion. There is local controversy over which of the rocks is actually Old Harry, but the consensus is that this honour belongs to the cylindrical stack that is furthest out to sea. However, within historical times there were other stacks further out than this one, which were given various names including “Old Harry’s Wife and Children”.
At low tide it is possible to walk along the shore from the north side, but walkers should beware of rock falls from above, given the process of erosion that is always taking place.
From the cliff top one can look across to the Isle of Wight and The Needles, which are also sea stacks carved out of chalk. At one time there was a continuous band of chalk between Old Harry and The Needles, before this was breached and the large expanse of Poole Bay was formed.
So who was Old Harry? One candidate for giving his name to the Rocks was the famous pirate Harry Paye, who was based in Poole Harbour and created havoc to Spanish and French shipping in the late 14th and early 15th centuries. Another possibility is that the name simply refers to the Devil, one of whose nicknames has long been Old Harry.
© John Welford
