Durdle Door, Dorset Stock Photography

Durdle Door Dorset. Durdle Door is a natural limestone arch on the Jurassic Coast near Lulworth in Dorset, England. The name Durdle is derived from the Old English 'thirl' meaning bore or drill. Hard layers of Portland Limestone have been folded on this part of the coast so that they appear almost vertical and these form the seaward edge of the small promontory here that includes Durdle Door. The impressive natural arch of Durdle Door formed due to the effect of the erosive power of the sea on the vertical layers of different types of rock. At some point in the past the sea would have begun to breach the hard Portland Limestone and form a string of caves along the coast.