Chapter 19 Earth s Interior Major Parts Crust Above the Moho Oceanic 8 to 10 km of basalt gabbro Continental 30 to 60 km of granite Mantle Moho to 2900 km Solid Rock Upper Moho to 410km Olivine pyroxene Transition Zone 410 670 km Silicate Spinels Lower 670 to 2900 km Perovskite periclase Core 2900 to 6367km Outer Core Liquid Metal Inner Core Solid Metal Earth s Interior Crust Oceanic Crust Basalt and Gabbro Thin 8 10 km Dense 2 9 3 1 g cm3 Young 250 my Continental Crust Granite Diorite Seds Thick 30 60 km Light 2 7 2 8 g cm3 Old 250 4000 my Mantle Upper Mantle Moho to 410 km Peridotite Olivine pyroxene Eclogite Pyroxene Garnet Transition Zone 410 670 km Spinels and Spinelloids Lower Mantle 670 2900 km MgSiO3 Perovskite MgO Periclase Core Outer Core 2900 to 5150km Molten iron metal 10 lighter element No S wave transmission Inner Core 150 6378 km Solid Iron Metal May slowly rotate relative to mantle How do we know what s there Seismology S wave shadow P and S reflections and conversions Meteorites Earth formed from primitive meteorites Xenoliths from kimberlites basalts Experiments Seismology S wave shadow No S waves opposite side earthquakes Core outer must be molten P and S reflections Discontinuities at 410 and 670 km Phase Changes P and S travel time anomalies Tomography Hot and cold regions Xenoliths Xenoliths are strange rocks Xenoliths are inclusions in kimberlites and basalts Xenoliths provide natural high pressure rocks Kimberlites bring diamonds and other rock samples from as deep as 670 km Basalts are derived from the lithospheric mantle Meteorites Meteorites tell us of Earth s bulk composition Chondrites are primitive meteorites Earth is chondritic Composition is similar to sun minus H He and other volatiles Experiments Multi Anvil Press Synthesis experiments to 1000 km depth Samples 1 5 mm3 Diamond Anvil Cell Spectroscopy Ultrasound X ray diffraction Convection in solid mantle Driven by U Th K decay internal engine Moves about 2 cm yr Causes earthquakes Move plates Splits and rejoins continents One Cell or two Magnetic Field Due to electrical currents from Earth s dynamo Convection in liquid metal outer core Convection is coupled to Earths rotation Field is subject to sporadic reversals Last reversal was 30 000 years ago Field hold ozone layer UV shield in place
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