Timeline 4.5 - 3.5 bya

• 4.5 bya - Earth forms
• 4.4 bya - First signs of water detected through zircon crystals, which were 4.4 billion years old and showed signs of H2O

  • 5% of the Earth's water came from meteors/asteroids, while the rest was from outgassing
  • Outgassing was similar to geysers
• 4.1 bya - Earth becomes colder, leading to prolonged thunderstorms due to the lower temperatures
• 4.0 bya - Significant changes on Earth:

  • Green oceans due to dissolved iron
  • Clumps of rocks/magma spread around
  • Red skies due to high levels of CO2 (carbon dioxide)
  • Over 70% of the surface coverage is water
  • The atmosphere was over 200 degrees Fahrenheit
  • Two main types of rocks: basalt and granite
  • Basalt rock is dark, very dense, and easily eroded
  • Granite rock is light, not dense, and hard to erode
• 3.5 bya - Key events:

  • Granite becomes widespread
  • Deep oceans form from pillow lavas around 3.5 bya
  • Stromatolites, rocky mounds created by small living organisms
  • Organisms found in shallow water, requiring photosynthesis which leads to the production of oxygen (O2)