What was first thought to be an underwater city off the coast of Greece has turned out to be a group of sedimentary deposits, formed by microbes living off of hidden methane jets.
It is not uncommon for microbes to turn sediment into concrete in the right environment (the term is called concretion), but it is unusual for it to happen this shallow.
“The site was discovered by snorkelers and first thought to be an ancient city port, lost to the sea,” Julian Andrews, a professor of environmental geochemistry at the University of East Anglia, said in a statement. “There were what superficially looked like circular column bases, and paved floors. But mysteriously no other signs of life – such as pottery.”
Some of the pavement-like features seen at the site. University of Athens
It was groups of archaeologists, geologists and professional divers from both Greece and the United Kingdom that were able to piece together the missing link. Though the entire area did look man-made, there were no clay pots or any other sign of human interference.
University of Athens
They examined the rocks themselves. “In this case the cement was an unusual mineral called dolomite which rarely forms in seawater, but can be quite common in microbe-rich sediments,” said Andrews. “These concretions were then exhumed by erosion to be exposed on the seabed today.”
Though there was excitement and buzz that we could have found an ancient, unknown civilization, it is also exciting that we have found evidence of microbes making brilliant, cylindrical and symmetrical structures.