VIII. Precambrian

1. Hadean - earliest formation stages
   1. cooling and solidifying
   2. completely unlike the modern Earth
2. Archean ( up to 2.5 b.y.) - transition into a modern, "real" planet
   1. formation of proto-continents
      1. processes
         • fast tectonics
         • accretion of arcs (fig. 19.3)
      2. rocks
         • greenstone belts (fig. 19.6)
           • ultra-mafic lava (1600 C)
           • pillow lavas
           • shale (argillite)
         • granite-gneiss complexes
           • granite intrusions
           • folded gneiss metamorphics
   2. formation of early atmosphere and oceans
      1. volcanic outgassing (fig. 19.15)
      2. comet contribution?
      3. produce free oxygen
         • processes
           • photochemical dissociation of water (fig. 19.16)
           • photosynthesis
         • results
           • BIFS (2.5-2by) (fig. 19.14)
           • red beds (1.8by and younger) (Proterozoic, not Archean)
3. Proterozoic - beginning of "modern" Earth
   1. stable continents and oceans
      1. quartz-carbonate-shale sequences (passive margins)
      2. ophiolites
      3. Rodinia - supercontinent (fig. 19.10)
   2. cratons
      1. shield
      2. platform
      3. mobile belts
   3. names (fig. 20.2)
      1. Baltica
      2. China
      3. Gondwana
      4. Siberia
      5. Kazakhstania
      6. Laurentia