12 Apostles (Princetown Vic - 16/05)

These are limestone stacks eroded by the ocean waves:
-Wave action erodes the cliff face, leaving harder rock as headlands.
-Waves eat away the rock at sea level, forming caves on each side of the
headland.
-The caves eventually meet up, forming an arch.
-The arch collapses, leaving a rock stack.
-Further undercutting by waves and opening up of vertical cracks in the rock
by rain and saltwater, gradually reduce the stack to a low platform or reef.
An easier example is the limestone cliff collapsing so that there was 12.