Durdle Door – the rock arch

Durdle DoorLocation: Durdle Door near Lulworth

Landform Type: Limestone

Age: Jurassic 140 million years old

Where to go:

Look out for: fossil ripple marks in the rock slabs at beach level, next to the arch. Donut shapes embedded in the rock around the top of the arch – these are remnants from a fossil forest!

The Rock Arch

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. The much softer rocks behind would have quickly been eroded away creating caves and natural arches. Eventually the arches collapsed leaving stacks, which would in turn be broken and washed away by the power of the waves. Durdle Door is part of only a small strip of hard Portland limestone that is left here. The remnants of old arches can still be seen in the form of 'stumps' of limestone only just visible in the waves. One day that is all that will remain of Durdle Door.