The Twelve Apostles are a collection of limestone rock stacks off the coast of Port Campbell National Park in Australia that were formed when erosion of the limestone cliffs by the Southern Ocean created caves that eventually collapsed, leaving tall rock stacks isolated from the shore. Known originally as the Sow and Piglets and later renamed the Twelve Apostles for tourism despite never having more than nine stacks, the limestone formations were created over 10-20 million years by erosion of the mainland cliffs.

1. The Twelve Apostles
Facts from Google and Wikipedia

2. The Twelve Apostles is a collection of limestone rock stacks jutting from the water in
Port Campbell National Park on the Great Ocean Road.

3. • Limestone cliffs
Created by constant erosion of the limestone
cliffs of the mainland beginning 10-20 million
years ago, the stormy Southern Ocean and
blasting winds gradually eroded the softer
limestone, forming caves in the cliffs.
The caves eventually became arches and when
they collapsed rock stacks up to 45 metres high
were left isolated from the shore.

4. • The site was known as the Sow and Piglets
until 1922 (Muttonbird Island, near Loch Ard
Gorge, was the Sow, and the smaller rock
stacks the Piglets) after which it was renamed
to The Apostles for tourism purposes. The
formation eventually became known as the
Twelve Apostles, despite only ever having nine
stacks.