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Summary from Previous Class
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Earth’s Internal Layering - Crust, Mantle and Core
Seismology, LVZ, Lithosphere, and
Asthenosphere
P,T, density variation in the earth’s interior
Transition Zone, Two-layered vs. whole mantle
convection
Plate tectonics, Plumes, Wilson Cycle, and recent
hypotheses by Anderson and Larson
Layer Names
Inner Core
Outer Core
Mantle
Crust
crust
Solid Iron
Molten Iron
Dense silicates
Great variety of minerals in the continental
crust but limited in the oceanic
Meteorite Types
Irons (Core Equivalent)
Stony Irons (Core/Mantle Boundary)
Stony meteorites
Achondrites (silicate dominated)
Chondrites (silicate)
Carbonaceous Chondrites (only type
with C & H2O…source of
LIFE!)
Meteorite composition and
abundance
Stony meteorites (92.8%)
Chondrites (85.7%)
Carbonaceous (5.7%)
ordinary (67.6%)
other (12.5%)
Achondrites (7.1%)
Ca-rich (4.7%)
Ca-poor (2.4%)
Stony irons (1.5%)
mesosiderites
pallasites
others
Irons (5.7%)
octahedrites
hexahedrites
ataxites
hydrated mins. (serpentine),
organic compounds, 1-9%H2O
pyroxenes, olivines, Fe-Ni metal
similar
pyroxenes,olivines,plagioclase
no plag
pyrox, plag, Fe-Ni
olivine, Fe-Ni
pyrox, oliv, Fe-Ni
kamacite, taenite
kamacites
taenite, kamacite
Source: Emiliani (1990) Planet Earth
Source of Meteorites
• Achondrites - from Mars & Moon
• Chondrites - stuff terrestrial planets are made
of
• Irons - Core of the earth
• Stony Irons - CMB
• The oldest meteorites are 4.5 billion years old
Achondrite
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Iron Meteorite
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Martian Meteorite
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Chondrule
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Olivine chondrule
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Pyroxene chondrule
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Composition of C chondrites
• The average Carbonaceous Chondrite
Weight%
• Carbon 2.0
• Metals
1.8
• Nitrogen 0.2
• Silicates 83.0
• Water
1- 9.0
Pb-isotope isochron for the age of the earth
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Earth as a Bar Magnet
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Polarity Time Scale
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Core Phase Diagram?
Core dT/dz
Depth (km)
Some Statistics…..
• OF ALL THE METEORITES THAT FALL
ON EARTH:
– 86% are Chondrites
– 7.1% are Achondrites
– 5.7% are Irons
– And 1.5% are Stony Irons