Old Harry Rocks are three chalk formations, including a stack and a stump, located at Handfast Point, on the Isle of Purbeck in Dorset, southern England. They mark the most eastern point of the Jurassic Coast, a UNESCO World Heritage Site. Location Old Harry Rocks lies directly east of Studland, about northeast of Swanage, and about south of the large towns of Poole and Bournemouth. To the south are the chalk cliffs of Ballard Down, much of which is owned by the National Trust. The rocks can be viewed from the Dorset section of the South West Coast Path. Formation The chalk of Old Harry Rocks used to be part of a long stretch of chalk between Purbeck and the Isle of Wight, but remained as a headland after large parts of this seam were eroded away. As the headland suffered hydraulic action (a process in which air and water are forced into small cracks by the force of the sea, resulting in enlarging cracks), first caves, then arches formed. The tops of the arches collapsed after being weakened by rainfall and wind, leaving disconnected stacks. One of these stacks is known as Old Harry. Old Harry's Wife was another stack which was eroded through corrosion and abrasion, until the bottom was so weak the top fell away, leaving a stump. Hydraulic action is the main cause of erosion (sheer force of the wave) that damaged the rock and caused it to fall away. Geology The downlands of Ballard Down are part of the of Portsdown Chalk Formation, containing some bands of flint, and were formed 72-84 million years ago in the Campanian age of the Late Cretaceous. The bands of stone have been gradually eroded over the centuries, some of the earlier stacks having fallen (Old Harry's original wife fell in 1509), while new ones have been formed by the breaching of narrow isthmuses. Across the water to the east The Needles on the Isle of Wight are usually visible. These are also part of the same chalk band and only a few thousand years ago were connected to Ballard Down. To form the stacks, the sea gradually eroded along the joints and bedding planes where the softer chalk meets harder bedrock of the rock formations to create a cave. This eventually eroded right through to create an arch. The arch subsequently collapsed to leave the stacks of Old