What are stromatolites?
Q: What are stromatolites?
A: Stromatolites are special rock-like structures that usually form in shallow water. They are formed by bacteria such as cyanobacteria, as well as other types of bacteria and single-celled algae. The mucus secreted by the bacteria collects grains of sediment, and they are stuck together with calcium carbonate from the bacteria, which builds up into the structures seen in certain sea-shore bays.
Q: How do cyanobacteria create their food?
A: Cyanobacteria use water, carbon dioxide, and sunlight to create their food.
Q: What is the significance of stromatolites?
A: The real significance of stromatolites is that they are the earliest fossil evidence of life on Earth. The oldest known stromatolites have been dated between 3,710 million years and 3,695 million years old.
Q: Where were the oldest known stromatolites found?
A: The oldest known stromatolites were found from an exposed outcrop of metacarbonate rocks in the Isua supracrustal belt (ISB) in Southwest Greenland.
Q: How did photosynthesis by early cyanobacteria affect Earth's atmosphere?
A: Early cyanobacteria in stromatolites are thought to be responsible for increasing the amount of oxygen in the primeval Earth's atmosphere through their continuing photosynthesis. This process eventually killed off most organisms which could not live in oxygen and led to today's environment where most organisms use and need oxygen - a process called the Great Oxygenation Event.
Q: When did this Great Oxygenation Event take place?
A: It took a long time for this event to take place - about a billion years after early cyanobacteria began performing oxygenic photosynthesis.
