Earth Subsystems

1. Atmospheric gases and precipitation contribute to weathering of rocks 3. Plant, animal, and human activity affect composition of atmospheric gases. Atmospheric temperature and precipitation help to determine distribution of Earth’s biota

5. Organisms break down rock into soil 5. Organisms break down rock into soil. Plate movement affects evolution and distribution of Earth’s biota. 6. Heat reflected from land surface affects temperature of atmosphere. Distribution of mountains affects weather patterns.

4. Plate movement affects size, shape, and distribution of ocean basins. Running water and glaciers erode rock and sculpt landscapes. 2. Evaporation, condensation, and precipitation transfer water between atmosphere and hydrosphere, influencing weather and climate and distribution of water.

7. Convection cells within the mantle contribute to movement of plates (lithosphere) and recycling of lithospheric material.

Atmosphere and Hydrosphere The interactions between the atmosphere and the hydrosphere have had a profound impact on Earth’s surface!

How did the Atmosphere Form and Evolve? Earth’s earliest atmosphere would be composed of hydrogen and helium, which would have been lost into space for two reasons: 1. Earth’s gravitational attraction was insufficient to retain light gases 2. Before Earth differentiated, it had no core or magnetic field

Once Earth had differentiated and a magnetosphere was present, the atmosphere began to accumulated as a result of outgassing involving the release of gases from Earth’s interior during volcanism.

These Archean volcanoes would have emitted: - Water vapour (most common) - CO2, SO2, CO, S8, H2, Cl2, N2 This early oxygen-deficient but CO2 rich atmosphere persisted throughout the Archean.

Atmosphere – Hydrosphere Connection Once the planet cooled sufficiently, water vapour (from volcanoes) condensed and surface waters began to accumulate. This may have happened before 4.0 Bya, but it had certainly happened by 3.8 Bya.

CO2 dissolved in oceans and was absorbed by chemical-weathering reactions on land – decreasing its atmospheric concentrations Nitrogen, which doesn’t react with other chemicals was left behind!

The remaining 2.4% is fresh water. Today -the great majority of Earth’s water – about 97.6% - is salt water. The remaining 2.4% is fresh water. Most of the fresh water is locked up in glaciers and ice caps!