Roughly one billion years ago, the town of Coromandel in the west of the Brazilian state of Minas Gerais was surrounded by the sea. The only living beings in existence were microorganisms that lived on the sea floor: cyanobacteria capable of carrying out photosynthesis, and archaea. Their metabolisms induced calcium carbonate precipitation, forming structures known as stromatolites. The stack of domes captured in the photograph above indicate the area was reasonably well protected, with waters that had a bottom current but no breaking waves. Hundreds of millions of years later, 10,000 years ago at most, water sculpted these rocks into caves.
Image submitted by paleontologist Fernanda Quaglio, a professor at the Federal University of São Paulo (UNIFESP), Diadema campusRepublish