Origin of the Atmosphere & Hydrosphere

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

http://www.earthref.org

Subduction ofocean crust

Na returned to crust in arc magma

Dehydration of ocean crust & melting

Some Na subducted into deep mantle