Geology
The Needles' pointed shape is a result of their unusual geology. The strata have been so heavily folded during the Alpine Orogeny that the chalk is near vertical. This chalk outcrop runs through the centre of the Island from Culver Cliff in the east to the Needles in the west, and then continues under the sea to the Isle of Purbeck, forming Ballard Cliff (near Swanage), Lulworth Cove and Durdle Door. It is also believed that The Needles were once connected to Old Harry Rocks (east of Studland and north of Swanage) where these strata lines moving from horizontal to near vertical can be seen from the sea.
Just off the end of the Needles formation is the Shingles, a shifting shoal of pebbles just beneath the waves. The Shingles is approximately three miles in length. Many ships have been wrecked on the Shingles.
Read more about this topic: The Needles