It Took Millions of Years for Australia’s Famous Twelve Apostles Landmark to Rise Out of the Sea
The iconic tourist destination provides a beautiful view, but also represents a physical record of Earth’s climate history
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In Victoria, Australia, the Great Ocean Road takes tourists past the “Twelve Apostles”—a collection of seven (confusingly, not a dozen) limestone rock stacks that stand 131 to 230 feet tall in the Southern Ocean, like puzzle pieces that drifted away from the equally dramatic coastline. About 2.2 million people visited the site in 2024, with experts estimating an increase to 3 million by 2032.
“Despite their ‘iconic’ status,” researchers write in a study published last month in the Australian Journal of Earth Sciences, “their geology is not well known.”
Lead author Stephen Gallagher and his team, however, shed light on how the distinctive landmark came to be. They found that tectonic plate movements raised the rock towers out of the water, and that their layers date back 8.6 million to 14 million years, making them younger than researchers had previously theorized.
“Early preliminary research indicated the ancient limestone layers ranged between seven to 15 million years old, but we discovered microscopic fossils that more accurately dated the layers as 8.6 to 14 million years old,” Gallagher, who is a researcher at the University of Melbourne interested in paleoclimatology and paleoenvironments, says in a statement.
It took millions of years for tectonic plates to push the rock layers that would eventually become the Twelve Apostles out of the water, but coastal erosion carved out the towers only in the last few thousand years, according to the study. In fact, only 20,000 years ago, the shoreline extended an extra 45 miles into the ocean from the Twelve Apostles, Gallagher tells the Guardian’s Petra Stock.
What’s more, the rock layers didn’t rise out of the sea perfectly horizontally. Tectonic plate movements tilted and broke the layers, and evidence of this is still visible in the cliffs around the Twelve Apostles, where visitors can see fault lines and tilted limestone layers.
The towers represent a physical history of more than just geological activity though. They are also one of the most well preserved and accessible records of the planet’s bygone climates and sea levels. "The layers in the rock, like tree rings, are environmental time capsules," Gallagher tells the Australian Associated Press’s Nick Wilson.
The landforms’ geological records include a period around 13.8 million years ago when the planet was significantly warmer than it is now. By studying the Earth’s past, researchers can predict future temperatures and sea levels within the context of climate change.
The team is currently working to study individual rock layers and reveal shifts in climate, ocean conditions and sea levels. The researchers aim to better understand how bygone processes impact coastal erosion today. But the stacks won’t be around forever. In 2005, one of nine towers collapsed, and a second went down four years later, leaving seven still standing.
“Just as scientists are racing to learn from disappearing glaciers, this study is a reminder that limestone stacks are also fragile archives of past environments,” Matej Lipar, a researcher at the Anton Melik Geographical Institute in Slovenia and an expert in stratigraphy who was not involved in the study, tells the Australian Broadcasting Corporation. The Twelve Apostles “preserve millions of years of evidence about changing seas, climates and landscapes.”/https://tf-cmsv2-smithsonianmag-media.s3.amazonaws.com/accounts/headshot/Margherita_Bassi.png)