Archean Eon

  • The beginning of lifeon Earth and evidence of cyanobacteria date to 3500 mya.
  • Life was limited to simple single-celled organisms lacking nuclei, called Prokaryota.
  • The atmosphere was without oxygen,and the atmospheric pressure was around 10 to 100 atmospheres.
  • The Earth’s crust had cooled enough to allow the formation of continents.
  • The oldest rock formations exposed on the surface of the Earth are Archean.
  • Volcanic activity was considerably higher than today, with numerous lava eruptions.
  • The oceans were more acidicdue to dissolved carbon dioxide than during the Proterozoic.
  • By the end of the Archaean, plate tectonicsmay have been similar to that of the modern Earth.
  • Liquid water was prevalent, and deep oceanic basins are known to have existed.
  • The earliest stromatolites are found in 3.48 billion-year-old sandstone discovered in Western Australia.
  • The earliest identifiable fossilsconsist of stromatolites, which are microbial mats formed in shallow water by cyanobacteria.