Origin of the Atmosphere & Hydrosphere• Gases escape from
Earth’s molten interior through volcanic activity.
• We observe this happening in the present, but most degassing occurred early in Earth history.
• Early atmosphere was probably CH4, NH3, (not oxidized), then CO, CO2, H2O through exchange with hot silicate rocks
Earth’s outgassing (and ingassing) continues in the present day.
Products of weatheringPrimary Residual DissolvedMinerals Minerals Ions
Feldspar Clay minerals K+, Ca+2, Na+
Aluminum hydroxide
Fe-Mg minerals Hematite & Mg+2
Limonite
Quartz Quartz Silica
Primary Solids that Ions that are carriedMinerals remain in soil away in water
----------Detrital sediments------------------ Chemical & biochemicalsediments
Average salinity = 34.5 per mil or 3.45 %
Sources:•runoff•groundwater
Sinks:•exchange with rocks at ocean ridges•exchange with sediments & formation of sediments•aerosols
Ion behavior:
•Conservative: changes with salinity only, by dilution
•Nutrient: used in metabolic processes
•Nutrient-related: mistaken for or accompanying nutrients
•Biolimiting: can be consumed completely by living things near ocean surface
Residence time = Total mass of element in reservoir (oceans)/influxGrams/(grams/year)
Al 8X10-4 0.8Pb 2X10-6 1.7Nd 4.2X10-6 1.9
Subduction ofocean crust
Na returned to crust in arc magma
Dehydration of ocean crust & melting
Some Na subducted into deep mantle