The Twelve Apostles are a collection of natural limestone stacks standing just off shore in the Port Campbell National Park, on the Great Ocean Road in Victoria, Australia.
Originally the site was called the Sow and Piglets. The name was changed in the 1950s to the more majestic "The Twelve Apostles" even though there were only eight remaining now.
Erosion of the Apostles
The stacks have been formed by erosion, and are varying heights and thicknesses. A number have fallen over entirely as waves continually erode their bases. A 50-metre tall Apostle collapsed on July 3, 2005.
BBC article about the collapse
The rate of erosion at the base of the limestone pillars is approximately 2 cm per year.
Can you see any changes from the photos on this page?
What is a Rock Stack?
A stack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast. Stacks are formed when part of a headland is eroded, leaving a small island.
They also form when a natural arch collapses due to sub-aerial processes and gravity. A stack may collapse or be eroded leaving a stump. Stacks form most commonly on chalk cliffs, because of the medium resistance to erosion. Cliffs with weaker rock such as clay tend to slump and erode too quickly to form stacks, while harder rocks such as granite erode in different ways. The sea attacks small cracks and opens them. The cracks then gradually get larger and turn into a small cave.
When the cave wears right through the headland, an arch forms. Further erosion causes the arch to collapse. This causes a pillar of hard rock standing away from the coast. This is called a stack.
Thanks to Wikipedia for this information.
How do you claim this EarthCache?
To claim this cache visit the above co ordinates. Please note the location is near some sheer drops, so stick to the pathway. You dont need to risk your life to do this cache.
(1) You will find an informative sign which of the numbered diagrams is a rock stack created. Email this to me, please don't include it in your log.
(2) Take a picture at this spot which clearly shows you with your GPS. Ensure the rocks stacks are visible in the background. Upload this with your log.
Please dont post any photos of sign in your log. Sorry but Logs that don't meet these requirements will be deleted.
Thanks to Alex Green the Park Ranger for permission in placing this EarthCache, we hope you have fun learning about the Apostles.