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Where do we start?
–Create the Universe
–Form the Earth and elements
–move the elements into their correct positions
–build the atmosphere and oceans
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The BIG BANG
• The Universe was created 15 billion years ago in one BIG BANG ...... How do we know?
• Start with the atom
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ENERGY
Nucleus
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ENERGY
Nucleus
} E = hv
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Elemental Absorption
• Every element has a characteristic absorption spectra - (ICP)
Wavelength400 nm 700 nm
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http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T014334A.gif
Spectrum of the Sun
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• From the magnitude of the shift we can calculate the speed of the star.
• The more distant stars are moving the fastest.
• From distance and velocity information -> TIME 15 billion years!
Wavelength
400 nm
700 nm
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At the Start
Big Blob of Neutrons (N)
Protons and
electrons
BANG
12 Minutes
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Now we are COOKING ........... Fusion produces heat
E = mc2
1 gram of hydrogen will produce 6.3x1011 j of heat.
Enough heat to boil 2 million liters of H2O
Compare this to our terrestrial energy consumption.
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C
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Elements H-1 through Fe-56
Supernovae
Explosion
Second Generation Star
H through Fe and n
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Elements H-1 through Fe-56
Supernovae
Explosion
Second Generation Star
H through Fe and n
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5
6
7
8
6 7 8 9
Pro
ton
Nu
mb
er
Neutron Number
14C
14Ne-
Beta Decay
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17
18
19
20
20 21 22 23
Pro
ton
Nu
mb
er
Neutron Number
40K
40Ar
e-
Electron Capture
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143
144
145
146
147
89 90 91 92 93
Pro
ton
Nu
mb
er
Neutron Number
234Th
238U
4He
Alpha Decay
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Review of Element Formation
• Big Bang
• Nuclear “Cooking” - Fusion
• Neutron Capture
• What is the end result?
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What about the Earth?
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Another look at the earth on a linear scale.
• Where did all the other elements go? H, He, C, N??
They got BLOWN AWAY
This leaves just Si, Mg, Fe, and O
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.....and just for fun
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Formation of the Earth• The earth started as a hot molten blob of metal and
oxygen
• As the blob cooled, density differences of the original components drove an elemental segregation.
• Metallic iron - The Earth’s core
• Mg, Fe, and Si oxides - The crust
• How do we know?
• We know from earthquake seismology
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A Slice of the Earth
Inner Core
Outer Core
Mantle
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A Slice of the Earth
Inner Core
Outer Core
Mantle
2900 km
• earthquakes travel as shear waves or compressional waves
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• shear waves only pass through SOLIDS (mantle)
• So we have a “liquid” iron core. This has important implications for other elements– Ni, S, Au, Pt, Ag, Pb dissolve in the liquid iron
• What is left is Mg, Si oxide mantle.
• The mantle is not really solid, but really a “putty” that is kept warm by the radioactive decay of 40K, 235U, 238U, and 232Th.
• The heating of the mantle drives convection cells.
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Inner Core
Outer Core
Lower Mantle
Crust
• The mantle melt cycle (subduction/formation) enriches the crust further in Si, Na, K, Ca, and Al
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What about the Oceans and the Atmosphere?
• The Earth is about 0.5% water. Where did it come from?
• The source of water in the early Earth is poorly understood ...we are lucky that it arrived.
• The gravitational attraction of the Earth retained almost all of the water.
• Surface water puts important constraints on global temperature! 0 <--> 100 oC.
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Controls on CO2
• CO2 is controlled by a global scale feedback loop with a time scale of >10,000 years
• Consider the following reactions:
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Controls on CO2
• CO2 is controlled by a global scale feedback loop with a time scale of >10,000 years
• Consider the following reactions:
Generic Weathering Reaction
Generic Precipitation Reactions
Generic Mantle Reactions
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AtmosphereAtmosphere
ContinentalContinentalCrustCrust
OceanicOceanicCrustCrust
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Lets work with units
CO2 (g) 0.0365 %, This is a mixing ratio
O2 20.95%
N2 78.08%
Ar 0.93%
PV= nRT, average mass gas 28.96 g/mol
%, 00/0, ppm, ppb
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Pressure
Atmospheric Pressure is a force: kg/m2
P0 = Mass(atm g)/4(r2
r = 6.37x106 m P0 = 101325 Pa
Ph = Po e -Mgh/RT
M = 0.029 kg/mol
R = 8.314 J/mol K
g = 9.81 m/s2
Scale height 5-6 km
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Unit Conversion
