Geological time periods

• Geological Time Periods

  • Eon
  • Era
  • Period
  • Epoch
  • Age
• 4 Eons

  • Hadean
  • Archean
  • Proterozoic
  • Phanerozoic
• How many Eras are there?

  • 10 Eras:
  • Paleozoic -> explosion of multicellular life, colonisation of the land by plants and animals, increase in oxygen concentration
  • Mesozoic
  • Cenozoic
• how many Periods are there?

  • 22 defined periods
  • Paleogene
  • Neogene
  • Quaternary
• how many Epochs are there?

  • 37 Epochs
  • Holocene
  • Pleistocene
  • Jurassic (Upper/Middle/Lower)
  • Triassic (Upper/Middle/Lower)
• what is the Current Geological Time?

  • Eon: Phanerozoic 538.8-0 Mya
  • Era: Cenozoic 66-0 Mya
  • Period: Quaternary 2.6-0 Mya
  • Epoch: Holocene 0.012-0 Mya
• define the Hadean Eon:[4540-4000 mya]

  • Earth is formed out of the proto-planetary disk
  • Secondary Collision with a Mars sized body, formed the moon
  • Earth has a highly unstable surface
  • Mantle convection currents, transporting molten rock to the surface and drawing heavier elements (Fe) to the core
  • The atmosphere was likely a mixture of hydrogen/helium with volcanic outgassing adding nitrogen and water vapour
  • Liquid water oceans form towards the end of the period
• Archean Eon [4000-2500 mya]

  • Geological Heat Flow increased compared to current eon
  • Residual heat from planetary accretion
  • Formation of the metallic core
  • Increased decay of radioactive elements (Half-life)
  • Reduced plate tectonics
  • Increase viscosity of mantle due to removal of water
  • Continents only appeared at the end of the Archean period
  • Atmosphere begins with 0.001% free oxygen compared to modern levels
  • Abiogenesis (The origins of life) began,due to Reduction in the harshness on Earth allowed for the formation of life, Multiple theories: Panspermia/Primordial Soup (Miller-Urey Experiment)
• Proterozoic Eon [2500-538.8 mya]

  • Beginning of the super-continental cycles and generation of mountains
  • Increased glaciation, Snowball Earth
  • Mass accumulation of oxygen in the atmosphere, Due to the exhausting of unoxidized sulphur and iron in the crust
  • Emergence of advanced single-celled eukaryotes
  • Evolution of symbiotic relationships: Mitochondria (nearly all eukaryotes), Chloroplasts (plants and some protists)
  • Increased biodiversity
  • Evolution of sponges, early bilaterians, cnidarians and sexual reproduction
• Phanerozoic Eon [538.8 – 0 mya]

  • Continued continental drift, forming and breaking apart the supercontinents of Gondwana and then Pangea
  • Mass and major glaciation events, due to global cooling events
  • Varied sea levels due to glaciation and overall global temperatures
  • Explosion of life (Cambrian Explosion), with increased diversity of life
  • Evolution onto land; from arthropods to dinosaurs to mammals
• Evidence for the Anthropocene Epoch

  • Increased radioactive elements in earth/water/air samples from nuclear weapons
  • Techno-fossils (plastics/metal constructs)
  • Desertification and irrigation of land masses
  • Rapid increases in global temperatures/sea levels/water acidification
  • Mass extinction of documented and undocumented species
  • Increased nocturnality of animal species