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Early Earth
…early bombardment…
…earliest phase of
Earth heating…
…near Moon…
…first seas…
…thin atmosphere of
H, CO2, H2O, N2, CO, NH3, CH4
Early
Bombardment
2 phases?
Relative dating
Early in Earth History the Planet
Developed a Magma Sea
4.5-4.0 billion years ago
Early Earth began to heat as the last extraterrestrial collisions subsided
1. Rock is a good insulator – stores heat
2. Collisions produced heat that was stored
3. Radioactivity
4. Gravitational contraction
What is the physical consequence of melting a homogeneous ball of rock?
Temperature reached melting point
of iron:
•Liquid iron flowed inward
•Friction raised temperature
•Liquid Silicon and Oxygen flowed
outward (Ca/Na/Al/K)
“Iron Catastrophe”
Planet became chemically
differentiated


Inner core –
Fe/Ni solid
Outer core –
Fe/Ni/Mg liquid
•Mantle – Fe/Mg solid rock
capable of flow
•Lithosphere – Fe/Mg/Si/O
•Lower lithosphere - Fe/Mg
•Crust – Si/O/Fe/Mg/Ca/Na/K/Al
•Oceanic crust – Fe/Mg/Ca
•Continental crust – Si/O/Na
Increasing Fe/Mg
toward core
Increasing Si/O
toward crust
Effect of
chemical
differentiation
Earth’s magnetic field
emanates from the
core complex and
surrounds the planet.
Magnetism gained
from early nebula is
magnified by turbulent
iron, nickel fluid of
Polarity + - tends to reverse and fluctuate with time
outer core.
Magnetic field
envelops entire planet
The “Bow Shock Effect”
Another consequence of differentiation is convection.
How does
convection
work?
How will the lithosphere respond to a plume?
The
continental
rifting
process
Mid-Ocean Ridge
Spreading Center
But if you keep making crust the Earth must be expanding! Right?
Spreading center and subduction zone
Global Tectonics
Partial Melting
Partial melting is responsible for evolving mantle rock…
among other things this gives us continents.
Continental lithosphere – general chemistry is
Si, O, Al, Na, K…in the form of a rock “Granite”
Oceanic lithosphere –
general chemistry is
Fe, Mg, Ca, Si, O in the form
of a rock “Basalt”
“Ridge Push”
“Slab Pull”
Plate
Movement
“Plate Drag”
Main Types of Plate Motion
Convergent
Divergent
Transform
Five types of
plate boundaries
Divergent
Transform
Convergent
•Ocean-Ocean
•Ocean-Continent
•Continent-Continent
Five types of
plate boundaries
Divergent
Transform
Convergent
•Ocean-Ocean
•Ocean-Continent
•Continent-Continent
Divergent
Boundary
Convergent
Boundary
Transform Boundary
Modern Earth
Pangea
240 million
Origin of India
Hot Spot
Paleomagnetism
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
The Rock Cycle