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Unformatted text preview: Mafic: 50% of silicon (o quartz or potassium feldsbar) Ultramfic: lack silicon About 2,900 km thick Largest layer by volume Peridotite rock Upper and lower mantle Lithosphere: rigid, brittle, non- flowable outer 100-150 km crust and top of mantle Asthenosphere: soft, ductile, flowable; between 150- 350 km mantle Occasionally deep sources volcanoes bring up pieces of the mantle called " Mantle Xenoliths" Mantle rocks are called Peridotites (August birthstone) Mantle ( very viscous (high viscosity means it resists flow) and mostly solid; upper mantle is less viscous)-Outer Core (2,900 to 5,155 km) mostly liquid iron Inner Core (5,150 t 6,370 km) Mainly solid iron Core-How do we know this? Planet Earth Page 2...
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- Spring '09