The discovery of what appeared to be mysterious structures in 20 feet of water off the coast of the Greek island of Zakynthos intrigued archaeologists, so they took a closer look … and were absolutely amazed at what they found.
No, tourists who were snorkeling near the island didn’t actually discover a lost city, even though the formations appeared to resemble cobblestones and cylinders built in ancient Greece. Instead, scientists think these structures were built entirely by tiny microbes, according to a University of East Anglia statement.
Archaeologists dove down to the “ruins” to take a look themselves after hearing the rumors from tourists. While the structures were intriguing, they noticed it lacked one feature: a complete lack of any indication that humans were ever there. That means no broken pottery, no coins, no nothing that would suggest a human settlement.
So they began looking at other options, and examined the mineral content of the structures. What they found is that they contained a mineral called dolomite — a byproduct of microbes that consume methane gas. This made the answer clear: it wasn’t an ancient city, it was an ancient leak of methane, and microbes had swarmed around these leaks and left their cement-like excrement all around it.
“We investigated the site, which is between two and five meters under water, and found that it is actually a natural geologically occurring phenomenon,” Lead author Prof. Julian Andrews, from UEA’s School of Environmental Sciences, said in the statement. “The disk and doughnut morphology, which looked a bit like circular column bases, is typical of mineralization at hydrocarbon seeps – seen both in modern seafloor and palaeo settings. We found that the linear distribution of these doughnut shaped concretions is likely the result of a sub-surface fault which has not fully ruptured the surface of the sea bed. The fault allowed gases, particularly methane, to escape from depth. Microbes in the sediment use the carbon in methane as fuel. Microbe-driven oxidation of the methane then changes the chemistry of the sediment forming a kind of natural cement, known to geologists as concretion.”