Very little free oxygen and few new minerals formed until the Great Oxidation Event 2.4 Bya caused by the development of cyanobacteria

• VOLCANOES

• 2.3-2.7: First free oxygen in the atmosphere. The first appearance of cyanobacteria (blue-green algae), they use energy from sunlight to split water (H2O) into Oxygen and Hydrogen (one proton and one electron). The cyanobacteria incorporate the electron into their system and release Oxygen back into the environment. It takes a large quantity of produced oxygen in order to get free oxygen O2 into the atmosphere. Oxygen readily forms compounds with other elements so all those other sources need to be oxygenated before

• 2.4: Banded iron formations (BIFs) exist through 1.8

HISTORY OF THE ATMOSPHERE

• 4.6 bya: H2, He, CH4 (Methane), NH3 (Ammonia), Nitrogen

• 4.0 bya: H2O, CH4, NH3, Nitrogen, CO2 (Carbon Dioxide)

• 3.0 bya: Nitrogen, CO2

• 2.0 bya: Nitrogen, CO2

  • 1.8 bya: Nitrogen, CO2, O* First Significant Free Oxygen in Atmosphere

• 1.0 bya: Nitrogen, Oxygen, CO2

• Present: Nitrogen Oxygen, CO2

Free oxygen results in the formation of many new minerals including clay minerals from the weathering of sillicates

1. Hydrosphere - Oceans, seas, glaciers, lakes, rivers, swamps, vegetation. Important factor in weathering of rocks, breaking down igneous and metamorphic rocks into sediment and transporting sediment into low lying areas (Basins) where new sedimentary rocks form. Glaciation is a significant sculptor and mover of rocks and sediments.

2. Atmosphere - evaporation of water leads to the formation of evaporite rocks and minerals.

   1. Troposphere 6-20 km. 78.08% Nitrogen, 20.95% Oxygen, 0.93% Argon 0.04% CO2

   2. Stratosphere 50 km

   3. Mesosphere 85 km

   4. Thermosphere 690 km

   5. Exosphere