summary from previous class 1.earth’s internal layering - crust, mantle and core 2.seismology,...
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Summary from Previous Class
1. Earth’s Internal Layering - Crust, Mantle and Core
2. Seismology, LVZ, Lithosphere, and Asthenosphere
3. P,T, density variation in the earth’s interior
4. Transition Zone, Two-layered vs. whole mantle convection
5. Plate tectonics, Plumes, Wilson Cycle, and recent hypotheses by Anderson and Larson
Layer Names
Inner Core Solid IronOuter Core Molten IronMantle Dense silicatesCrust Great variety of minerals in the
continental crust but limited in the oceanic crust
Meteorite TypesIrons (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%) hydrated mins. (serpentine),
organic compounds, 1-9%H2O ordinary (67.6%) pyroxenes, olivines, Fe-Ni metal
other (12.5%) similarAchondrites (7.1%)
Ca-rich (4.7%) pyroxenes,olivines,plagioclaseCa-poor (2.4%) no plag
Stony irons (1.5%)mesosiderites pyrox, plag, Fe-Nipallasites olivine, Fe-Niothers pyrox, oliv, Fe-Ni
Irons (5.7%)octahedrites kamacite, taenitehexahedrites kamacitesataxites 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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Pol
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Tim
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Cor
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Cor
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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
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