stromatolite

/stroʊˈmætəlaɪt/
noun
  1. A layered rock-like structure formed by the growth of tiny organisms called cyanobacteria (blue-green algae) in shallow water, often found as fossils from ancient times.
    • Tourists visited the lake to see living stromatolites growing in the shallow water.
    • The oldest fossils on Earth are stromatolites, dating back over three billion years.
    • Scientists study stromatolites to learn how early life shaped the planet's environment.
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