NORWICH, ENGLAND—Scientists from the University of Athens and the University of East Anglia say that what looked like the paved floors, courtyards, and colonnades of a lost city in shallow waters off the coast of the Greek island Zakynthos were actually created by a natural geological phenomenon up to five million years ago. According to a report in Tech Times, Julian Andrews of the University of East Anglia noticed that there wasn’t any pottery or other signs of human activity around the supposed ruins, which were discovered by recreational divers. The researchers took a closer look at the mineral content and texture of the stones with X-rays, microscopy, and stable isotope techniques. They think the column-shaped concretions are the result of mineralization at hydrocarbon seeps along a fault under the seabed. Microbes in the seafloor sediments used the methane and other gases from the fault as fuel, changing the chemistry of the sediment and forming the concretions. Erosion eventually exposed and shaped the concretions. “This kind of phenomenon is quite rare in shallow waters,” Andrews said. “Most similar discoveries tend to be many hundreds and often thousands of meters deep underwater.” For more, go to "Greece's Biggest Tomb."