The limestone stacks of the Twelve Apostles, which jut out of Victoria’s cold surf on the Great Ocean Road, are among the state’s most popular tourist attractions: in 2019, 2.8 million people made the winding pilgrimage to look at them.The Twelve Apostles on Victoria’s Great Ocean Road show millions of years worth of changing climates.Gallagher, a micropalaeontologist at the University of Melbourne, does not see rock. He sees time.
That makes the Apostles geological records of the ocean – its chemical make-up and what was living in it – from between seven and 15 million years ago.“What I see in something like the rocks of the Twelve Apostles is almost like a library, a history of what’s happened,” says Professor Alan Collins, who studies the evolution of the deep Earth at the University of Adelaide.
“They are on all the tourist brochures. You’d imagine everyone knows everything about the layers – but it turns out there’s virtually nothing.”Each layer of limestone represents a few tens of thousands of years; an entire stack records many millions of years of history, a length so vast – modern humans are just 315,000 years old – geologists call it “deep time”.