A famous natural arch and a beautiful secluded cove; their existence owed to the collision of continents and the birth of the Alps. If you visit Durdle Door and Lulworth Cove, look carefully and you will notice that the layers exposed in the cliffs are tilting steeply to the north. This is most notable with Durdle Door itself as it is formed from a layer of hard limestone standing almost vertically out of the sea. Normally layers of limestone would be horizontal. Only the most fundamental force in geology could have altered these rocks in this way – plate tectonics.