Note the layers of rock in this Stromatolite.
. As the sticky algae grew, they trapped sand and other sediment and other layers would grow. The organisms grew quite large over hundreds of years. Over time they became fossilized. Since cyanobacteria are able to photosynthesize, scientists believe that these primative algae may have been responsible for putting the first oxygen into the Earth's atmosphere. Many of these fossils are over 3 billion years old!
were found in a limestone rock at Haw Ridge in Oak Ridge.
