_02_EarthInterior

_02_EarthInterior - GEL 1: Lecture 2: Interior of the Earth...

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GEL 1: Lecture 2 : Interior of the Earth (Ch. 2 & pp. 350-361, read selectively – if you see words and concepts that don’t sound familiar, don’t worry about it. Just focus on the parts of the text that are included in the notes and therefore were discussed in class.) Interior of the Earth Earth, having differentiated early in its history like the rest of the planets, is composed of an interior core , a thick mantle and thin, outer crust . - radius of the Earth is 6371 km The composition of the Earth, derived from the constant addition of material from the solar nebula by collisions early in its history, is dominated by iron (35%), oxygen (30%), silicon (15%), and magnesium (10%). - because of differentiation early in Earth history, these elements are unevenly distributed throughout the planet. - much of the iron collapsed toward the interior to become the metallic core, while silicon and oxygen combined to create the molecule SiO 2 ( silica ), the main component of silicate rocks that dominate the rocky mantle and crust. So Earth is mostly composed of metallic iron and silicate rock . . . Pressure increases constantly with depth in the Earth because of compression caused by the weight of overlying rock. Density increases toward Earth’s interior, partly due to increasing pressure and thus tighter packing of molecules within rock and partly due to the change in composition at the core-mantle boundary to denser metallic iron Temperature also increases toward the center of the Earth. This rate of change in temperature with depth is known as the geothermal gradient . - temperatures at the center of the Earth are estimated by mathematical models to be about 4700°C, slightly less than the temp. of the Sun's surface. Layers of Earth based on composition: Inner core is solid, outer core is liquid, both composed of very hot, very dense (~10-13 g/cc), metallic iron with small amounts of nickle and sulfur. (You don’t have to memorize the absolute densities – just knowing that density increases toward the center of the planet is enough) The solid inner core is almost pure crystalline iron almost as hot as the surface of the sun but “frozen” at the center of the planet by the intense pressure. The liquid outer core is a dense sea of molten iron with traces of other metals (iron alloy). The flow of liquid iron in the outer core generates Earth's magnetic field that shields it
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_02_EarthInterior - GEL 1: Lecture 2: Interior of the Earth...

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