|Geology: Stromatolites are fossil algae, sometimes called “picture algae,” that thrived in warm aquatic environments and built reefs similar to today’s coral. The specimens below from England, with their unique pictures created by algae in limestone, are over two billion years old. As well as being the oldest record of life on earth that can be seen without magnification, stromatolites are also the longest living forms of life on this planet. They can be traced back 3.5 billion years to the early Archean eon. The photosynthesizing cyannobacteria that formed the stromatolites’ colonial structures are believed to have been responsible for the creation of the earth’s oxygen atmosphere. They were the dominant life form on earth for over two billion years. Now nearly extinct, modern stromatolites were first discovered in Australia in 1956. They live a precarious existence in only a few localities worldwide. Known locations include the thermal springs of Yellowstone National Park, lakes in Antarctica, and the ocean off the Bahamas.