Formed 25 million years ago when African and European tectonic plates collided. Carved to today’s appaerance by the sea creating an arch ‘door’.
The origin of Durdle Door probably began as a notch in a point of weakness in the wall of Portland Limestone that faced the onslaught of the sea. Over time, this small notch was subject to constant battering by the sea and widened to form a cave. Once the waves broke through the back wall of the cave, they would have eroded away the weaker rocks behind and over time the sweeping beach would have formed in that space. The cavity in the wall of limestone would have become larger to eventually form the freestanding natural arch that we see today.
THE INEVITABLE FUTURE OF DURDLE DOOR
Eventually physical weathering processes combined with chemical weathering processes (limestone is particularly prone to solution weathering in coastal environments) will weaken the structure so that it is unable to support the upper bridge.
This will collapse and leave behind a freestanding limestone pillar which over time will erode away and leave a stump.
On the 8th March 2017, the unthinkable happened to one of Malta’s most iconic natural monuments. The Azure Window, a natural limestone coastal arch, which formed the backdrop for scenes in Clash of the Titans, the Count of Monte Cristo and Game of Thrones collapsed after a violent storm.
The Prime Minister, Joseph Muscat said the news was heartbreaking and he commented that “reports commissioned over the years indicated that the landmark would be hard hit by unavoidable natural corrosion”.
https://jurassiccoast.org/news-events/future-durdle-door/?fbclid=IwAR0eD43vAuKJAIag82bPYbOwyXOWafrVup8FYG3cHdOWFAcJWIlNTiDT5P0
