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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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