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
E = hv
Nucleus
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400 nm
Wavelength
700 nm
Elemental Absorption
• Every element has a characteristic absorption
spectra - (ICP)
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Spectrum of the Sun
http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T014334A.gif
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700 nm
Wavelength
• 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!
400 nm
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At the Start
Big Blob of
Neutrons (N)
BANG
Protons
and
electrons
12 Minutes
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1H
9
and -10e
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1. Cloud of protons and electrons
2. Fusion of Protons:
1
1H
4 11H + 2-10e Þ 42 He + 6 g
and -10e
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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1. Cloud of protons and electrons
2. Fusion of Protons:
1
1H
4 11H + 2-10e Þ 42 He + 6 g
and -10e
3. Fusion of Helium nuclei :
4
2 He
+ 42 He Û
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4 Be
8
4 Be
+ 42 He Û
12
6C
12
C
6 Be
11
+ 42 He Û
16
8O
+ g
+ g
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1. Cloud of protons and electrons
2. Fusion of Protons:
1
1H
4 11H + 2-10e Þ 42 He + 6 g
and -10e
4. Fusion of carbon nuclei :
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11Na
12
6C
+
12
6C
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10 Ne
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12 Mg
+
1
1H
+
4
2 He
+g
• This process stops at iron-56
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3. Fusion of Helium nuclei :
4
2 He
+ 42 He Û
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4 Be
8
4 Be
+ 42 He Û
12
6C
12
6 Be
+ 42 He Û
16
8O
+ g
+ g
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Supernovae
Second Generation Star
Elements H-1 through Fe-56
Explosion
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H through Fe and n
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Supernovae
Second Generation Star
Elements H-1 through Fe-56
H through Fe and n
Explosion
0 e Þ 4 He
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H
+
2
1
-1
2
1H + 12 C Þ 13 C +
1
6
6
+ 4g
0b +
1
13C + 4 He Þ 16 O + 1n
6
2
8
0
56 Fe + 1n Þ 57 Co + 0b
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0
27
-1
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Beta Decay
Proton Number
8
e14N
7
14C
6
5
6
7
8
9
Neutron Number
16
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Electron Capture
Proton Number
20
e19
40K
18
17
20
40Ar
21
22
23
Neutron Number
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Alpha Decay
Proton Number
147
146
238U
145
4He
144
143
234Th
89
90
91
92
93
Neutron Number
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Review of Element Formation
•
•
•
•
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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
2900 km
Mantle
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• 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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Crust
Lower
Mantle
Outer
Core
Inner
Core
• 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
CaSiO 3 (Wollastonite)
3H 2O + 2CO 2 + CaSiO 3 Þ Ca 2+ + 2HCO -3 + H 4SiO 4
Foraminifera (bugs)
Generic Precipitation Reactions
Ca 2+ + 2HCO -3 Þ CaCO 3 + CO 2 + H 2 O
Diatoms (more bugs)
H 4SiO 4 Þ SiO 2 + H 2O
CaCO3 + SiO 2 Þ CaSiO 3
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+
CO2
Generic Mantle Reactions
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Atmosphere
3H 2 O + 2CO 2 + CaSiO 3 Þ Ca 2+ + 2HCO-3 + H 4 SiO 4
CaSiO 3
Ca 2 + + 2HCO -3 Þ CaCO 3 + CO 2 + H 2 O
H 4SiO 4 Þ SiO2 + H 2 O
Oceanic
Crust
Continental
Crust
CaCO 3 + SiO 2 Þ CaSiO 3
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+
CO2
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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(pi)r2
r = 6.37x106 m P0 = 101325 Pa
Ph = Po e -Mgh/RT
æ Mgö
Ph
ln( o ) = -ç
÷h
è RT ø
P
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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
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