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1-Observational evidence for relative abundances (earth) (Composition…
1-Observational evidence for relative abundances (earth)
Relative abundances
Plot is logarithmic so that Silicon has an abundance of 10^6
Experimental evidence from physical sources
Composition
Not homogeneous
Layers of increasing density towards the core
can only access the atmosphere, oceans and crust
See diagram for more
Crust is silicates
Mantle is olivine rock
Core solid iron or iron-nickel
Supported by density, elastic properties and seismic activity
Earthquakes
Body waves
P-waves
Longtitudinal
Slower
Sound waves in air
Cause ground to be compressed and dilated in direction of travel
Less destructive
Primary waves
S-waves
Opposite to s
Secondary waves
greater amplitude
Only travel through solids
Travel through interior of earth following ray paths deflected by different densities and compositions
Surface waves
Like water waves
Low frequency
Large amplitude
long duration
Rayleigh waves
Cause horizontal shears
Love waves
Cause ground roll, like ripples on water
Goldschmidt Classifications
Atmophiles
(mostly gases)
H,C,N and noble gases
not oxygen, since oxygen occurs as silicates
Lithophiles
Silicate phase
Li,Na,K,Mg,Si
Chalcophiles
Sulphide phase
Cu,Zn,Hg,Pb,Bi
siderphiles
Iron phase
Fe,Ni,Co,Au,Pd
Readily dissolve in molten iron
Blast furnace model
based on thermal history
assumes earth formed 4.5 Gyr ago
was molton at some point
heat from GPE (accretion) and radioactive heating
Causes separation, similar to the effects seen in blast furnaces