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Geologic Time Scale

  • Phanerozoic 542mya to present

    Not many life forms until very end.
  • Paleozoic 542mya-251mya

    Evolution of fish, insects, and reptiles.
  • Cambrian 542mya-488mya

    Marine intertebrates evolve.
  • Ordovician 488mya-443mya

    Condonts, ostracods, algae, and seaweeds evolve.
  • Ordovian Mass Extinction

    Thought to be caused by a drop in sea levels as glaciers formed. The followed by rising sea levels as glaciers melted. (Ice Age)
  • Silurian 443mya-416mya

    First air-breathing animals evolve.
  • Devonian 416mya-359mya

    Fish, amphibians, and ammonites evolve.
  • Devonian Mass Extinction

    Some theories include change in sea level, asteriod impacts, climate change, and new plants chaning soil.
  • Carboniferous 359mya-299mya

    Land covered in forests so insects evolved and became very large.
  • Permian 299mya-251mya

  • Mesozoic 251mya-65mya

    Dinosaurs lived during this time.
  • Triassic 251mya-199mya

    Dinosaurs begin to evolve, while dicynodonts become extinct.
  • Permo-Triassic Mass Extinction

    Earths biggest mass-extinction. Theories are the comet and asteriod hitting earth, volcanic eruption, and loss of oxygen in sea levels.
  • Jurassic 199mya-145mya

    Dinosaurs flourish and become very large. Conifers grow.
  • End-Triassic Mass Extinction

    Caused by massive floods of lava, breakup of pangea, and opening of Atlantic Ocean.
  • Cretaceous 145mya-65mya

    End of age of reptiles. Evolution of modern insects and flowering plants.
  • Cretaceous-Tertiary Extinction

    Caused by gradula climate change or volcanic eruptions.
  • Cenozoic 65mya-present

    Mammals evolve. Along with humans.
  • Paleogene 65mya-23mya

    Evolution of birds, mammals, and various forms of humans.
  • Neogene 23mya-2.5mya

  • Quaternary 2.5mya-present

    The last two million years. Mammals are dominant.
  • Sixth Mass Extinction

    Said to be caused by humans. To happen in the future. Claimed to be the largest yet.