Easy Science: simple timeline of pre-Cambrian earth and life

Understanding the formation of the earth can be overwhelming. I've simplified and condensed the big events into an easy-to-follow timeline. Obviously, the list is not meant to be exhaustive and probably isn't 100% accurate. Clicking on the links will take you to Wikipedia that lead to journal articles (a few links directly to sources).

Pre-Earth: The universe starts with the Big Bang 13.8 billion years ago.

Earth

  • Hot Earth: earth covered in molten rock
    Zircon crystal.

    Zircon crystal.

    • 4.6 bya: halo of debris (from Big Bang) around sun
      • Particles collide to form larger masses until spheroid planets form
    • 4.5 bya: Mars-sized planet Thea collides with Earth then becomes moon
      • Moon 10x closer + shorter days (earth rotating faster) = lava tidal waves every 6 hours?
    • 4.4 bya: some crust (evidence: Zircon crystal)
  • Cool Earth
    • 4.3 bya: lots of crust, oceans [disputed]
      heavy_bombardment

      Late Heavy Bombardment.

    • 4.0~3.8 bya: Late Heavy Bombardment
    • 4.0 bya: lots of crust (Canadian gneiss)
      1. At first, surface of earth so hat that lava stays molten at surface
      2. Eventually, earth cools; rafts form
      3. Ultramafic crust develops; ultramafic eruptions occurring; mantle composition not changing
      4. Surface temperature drops; crust gets thicker; ultramafic magma gets trapped; cools, fractionalizes; mafic eruptions
      5. Plates form, cool subduct; flux melting causes felsic eruptions
    • 3.8 bya: oceans
    • 2.3 bya: Great Oxidation Event

Life

  • Prokaryotes
    • 4.3 bya: Light carbon (C12) diamond inclusion in Jack Hills, Australia [disputed]
      • Believed that photosynthesis is the only way to produce C12, but other processes have been discovered
    • 3.5 bya: Cyanobacteria fossil in Apex Chert, Australia [disputed]
      • Chert embedded in volcanic rocks where cyanobacteria might not live; could be inorganic erosional features (microcracks), which have been found in other chert
    • 3.2 bya: Stromatolites in Pilbara, Australia
  • Eukaryotes
    bangiomorpha

    Bangiomorpha fossils from Butterfield (2000).

The material came from my lecture notes for EOS 204L, Duke University, Spring 2014, and is not necessarily accurate or up-to-date.

Click here or here for interactive timelines of Earth's history.

Cortney

About Cortney

Geology lover. Proud owner of a 2014 Honda CRF250L. Grew up on NES, N64, & Gameboy. Collects maneki neko (lucky cats). Married to a gearhead. Email cortney@luckysci.com. Wishlist.

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