Earth History

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Slide 1

Atmospheric Chemistry

Formation of the Atmosphere

The Early Atmosphere

Origin of Life and Oxygen

Ozone

Air Pollution

Acid Rain

Greenhouse Effect

Slide 2

Formation of the Earth

Apollo Space Program (1960’s)

Otto Schmidt

Cosmic Dust Planet (100 million years)

Ball 10 km 12,000 km

Heat Generated during the Process

( Collisions )

Differentiation Occurs

Slide 3

Thermal Consequences

Earth’s Core

Molten Fe ( Density 7.86 g/cc)

Ni ( Density 8.9 g/cc)

Outer Shell

Fe2O3 / FeO ( Density 5.2/5.7 g/cc)

Si/SiO2 (Density 2.33/2.32 g/cc)

Al/Al2O3 ( Density 2.7/3.5 g/cc)

Slide 4

Formation of the Mantle

The less dense material will go toward the surface (Polar Oxides of Si, Al, Fe)

Separation will occur as Fe/Ni core is nonpolar

MANTLE

starts to form and cool

(Production of Iron from Iron Ore)

Slide 5

Isotope Distribution of the Earth

Investigation of the History of the Earth primarily relied on isotope analysis.

Decay of 238U 206Pb

Decay of 235U 207Pb

And the rare gases He, Ar, Xe

 4.5 Billion years Old

Slide 6

Appearance of the Atmosphere

Did the atmosphere suddenly appear ?

Isotope Analysis gives a clue

Claude Allegre He, Ar & Xe

( Rare Gases do not react readily )

Argon has three isotopes

(36Ar 0.337) (38Ar 0.063) (40Ar 99.60) EC Decay 40K 40Ar

( t1/2 = 1.28 x 109y )

Slide 7

Isotopes of Xe

Xenon has 9 isotopes

With the following distribution

124Xe 0.1% , 126Xe 0.09%, 128Xe 1.91% 129Xe 26.4%, 130Xe 4.1%, 131Xe 21.2%

132Xe 26.9%, 134Xe 10.4%, 136Xe 8.9%

Slide 8

Distribution of Xe isotopes

Nucleosynthesis gives rise to 129Xe

- Decay of 129I 129Xe

(t1/2 = 1.6 x 107y)

The distribution of Xe isotopes in the mantle and atmosphere can give information about the Earth’s Atmosphere as the outgassed distribution will vary to that of the mantle.

Slide 9

Differentiation

The Atmosphere was formed due to

OUT GASSING of the mantle (Heat)

& Volcanic Activity