Scientist have just extended the range of Australia’s iconic Twelve Apostles. In a recent discovery, University of Melbourne PhD student Rhiannon Bezore discovered five interesting limestone stacks 50 meters (165 feet) under water.
Rhiannon found the “drowned” limestone stacks when you she analyzing sonar data, as part her PhD project to survey potential reef habitats along the coast. The new Drowned Aspotles sit in front of a submerged ancient coastal cliff about 6km offshore of the Twelve Apostles on Victoria’s southern coast.
“We are calling them the Drowned Apostles because if you had stood on this ancient cliff face over 20,000 years ago they would have looked largely the same as the current Twelve Apostles,” says University of Melbourne coastal geographer David Kennedy, who is supervising Ms Bezore’s PhD work.
Normally these type of limestone structure should be completely eroded, however Professor Kennedy suggests they could have been submerged by rising sea levels. According to Associate Professor Kennedy, the most likely explanation is that at the end of the last ice age, around 20,000 years ago sea levels rose so fast as the ice melted that the stacks were simply swamped in place.
“Sea levels probably rose at the end of the last ice age so quickly that the sea just ran across the top of these things without knocking them over,” says Associate Professor Kennedy, from the School of Geography. “It is amazing that they survived.”
The research has been published in the US-based Journal of Coastal Research and presented at the International Coastal Symposium at Coogee in Sydney.
Following the The limestone cliffs being eroded by crashing waves we can see how the Drowned Apostles fall in line with their 12 cousins. The ”drowned” stacks are made of the same eroded limestone as the seaside Twelve Apostles
“As the drowned Apostles are found in the same geological setting as the current Twelve Apostles, it is reasonable to assume that they were formed under the same geomorphic processes, some 60,000 years apart,” the researchers say in the journal article.
Through erosion the height of the Drown Apostles was warn down below the height of the Tweleve Apostled, suggesting that the sunken stacks had stood for much longer under eroding conditions before they were submerged still intact. They now stand up to nearly 7m tall compared to the Twelve Apostles that range from 30m to 67m tall.
[University of Melbourn]
