9/27/2015 10:55:00 PM
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Planetary Volcanism
9/22
 More iron = more dense core
 Earth structure
o Earth is about half core
o D”
 Between outer core and mantle
 Particularly hot and bumpy
 Birth place of plumes
 Source for convection
o Convection
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Subduction zones putting cold stuff into mantle (only on
earth elsewhere stuff drips off the bottom)
Heat from the D” rises
Convection hits conduction at the lithosphere
 Lithosphere cooling by conduction
 Earth is a mobile lid planet (cooling more
efficiently) if convection stopped we could
become a one plate planet
 Others are one plate planets
Asthenosphere
 Water entering it
 Makes it more brittle
 Low velocity and low viscosity
 Allows lithosphere to move
 Venus is missing this
o Hotspots
 Any planet that’s hot will have these
 Hawaii
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Can see plate movement through these
 Large Igneous Provinces
o Temperature of the convecting mantle
 (dt/d2)= &gT/Cp
0.3 K/Km2 – 1.0 K/Km2
 & Thermal expansion 3x10^-5 K^-1
 Cp Heat capacity 1kJ^-1 K^-1
 Mantle is Adiabatic (d2)
 Function of the temperature of the mantle
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Can find potential temperature by extrapolating
the adiabatic
The more Mg in your basalt the hotter the melt has to
be
Inner Mantle solid because of pressure
 Pressure too high for rocks to disassociate
 line between melt and no melt is called the
solidus
Get melting by
 Adding volatiles (water)
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Decreasing pressure
Or increasing heat
9/27/2015 10:55:00 PM
9/27/2015 10:55:00 PM