Early Earth…earliest phase of Earth heating…

…first seas…

…thin atmosphere of H, CO2, H2O, N2, CO, NH3, CH4

…early bombardment…

Early Bombardment

2 phases?

Relative dating

Early Earth began to heat as the last extraterrestrial collisions subsided1. Rock is a good insulator – stores heat2. Collisions produced heat that was stored3. Radioactivity4. Gravitational contraction

Earth Developed a Magma Sea4.5-4.0 billion years ago

What is the physical consequence of melting a ball of rock with many different types of elements and compounds?

Temperature reached melting point of iron:

• Liquid iron flowed inward• Friction raised temperature

• Less dense compounds flowedoutward (SiO2 and others)

“Iron Catastrophe”

Planet became chemicallydifferentiated

Fe/Ni

Fe/Mg

IncreasingFe toward

core

IncreasingSi towardsurface

There are certain trends in Earths chemistry.The crust is relatively depleted in Fe, Mg and enriched in Si, O

Effect ofchemical differentiation

There are certain trends in Earths chemistry.The crust is relatively depleted in Fe, Mg and enriched in Si, O

Earth’s magnetic fieldemanates from the core complex and surrounds the planet.

Magnetism gained from early nebula ismagnified by turbulentiron, nickel fluid of outer core.

Magnetic field envelops entire planet

Polarity + - tends to reverse

and fluctuate with time

Earth is probably not built ofuniform layers, it is likely mixed

somewhat by convection

MANTLE PLUMES warm rock rises,

cool rock descends

How will the lithosphere

respond to a plume?

The continental

rifting process

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