The Twelve Apostles

The Twelve Apostles are a group of limestone sea stacks standing offshore along the Port Campbell coastline of Victoria, Australia, part of the Port Campbell National Park, carved from Miocene-age limestone cliffs roughly 10 to 20 million years old. They formed through ongoing coastal erosion, as wave action attacked weaknesses in the soft limestone cliff face, first hollowing out caves, then widening these into arches, and finally collapsing the arches to leave isolated pillars of rock standing separately in the sea while the cliff line retreated landward behind them. Despite the name, only a handful of the stacks were ever actually standing at once, and several have collapsed in recent decades, including one in 2005, illustrating that the formation, like the cliffs that produced it, is a continually evolving and ultimately temporary feature of the coastline.