Dorset — a bird’s eye view — Lulworth Cove
Photograph by Grahame Austin of Kitchenham Photography; text by John Chaffey
Published in June ’09
Lulworth Cove is one of the most well-known landmarks of the World Heritage Jurassic Coast Site, and this photograph shows it in its setting on this east-west stretch of the South Dorset Coast. The section of coast shown in the photograph extends from just east of the eastern enclosing arm of Lulworth Cove, at the bottom of the image, to the west at Durdle Promontory at the top of the photograph.
The geology of this section of coastline has a fundamental influence on the nature of the coast. The Jurassic and Cretaceous strata run in a series of outcrops parallel to the coast, producing what is known as a concordant coast. The most seaward of the outcrops is that of the Jurassic Portland Limestone, dipping inland, which forms the clear cliff barrier that is breached at Lulworth Cove, at Stair Hole just to the west and in the west at St Oswald’s Bay and Man o’ War Bay at the top of the photograph. Durdle Promontory beyond Man o’ War Bay is also built mainly of Portland Limestone. Inland from the Portland Limestone is the outcrop of the mainly Cretaceous Purbeck Beds, mostly shales and limestones, which form reefs running out into Lulworth Cove, shown as dark shadows on the photograph. The Purbeck Beds also appear in the sides of Stair Hole. Further inland is the outcrop of the Wealden Beds, which are mainly sands and clays, with some grit bands. These beds form the low cliffs at the eastern and western ends of Lulworth Cove, and also the low cliffs at the western end of Man o’ War Bay at the top of the photograph. Chalk is the most landward of the strata exposed along this coast. It forms the cliffs at the inland side of Lulworth Cove and also forms the cliffs of St Oswald’s Bay and Man o’ War Bay on the seaward side of Hambury Tout, which is ascended by the well-marked path that rises from the car park at Lulworth Cove.
At one time the small stream that runs through the lower part of the village of West Lulworth (seen on the image) flowed through the present Lulworth Cove and out through the gap between what are now the enclosing arms of Lulworth Cove. It is thought that rising sea levels in post-glacial time would have drowned the lower part of this valley. The sea would then have had access to the lower land underlain by the Wealden Beds, and would have begun to erode in these softer rocks the beautifully curved outline of Lulworth Cove. The tougher, more resistant Chalk has not eroded so quickly and thus forms the high cliffs along the inland side of the Cove.
Stair Hole has been formed by the sea breaching the barrier of Portland Limestone and then eroding away the less resistant Purbeck Beds and the Wealden Beds on the landward side. A similar process was responsible for the opening up of St Oswald’s Bay and Man o’ War Bay, with the surf-edged Man o’ War rocks being the remnants of the Portland Limestone barrier.