F13 quiz 1 condensed notes

We postulate that when the sun condensed enough to

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Unformatted text preview: ck and metal but relatively little volatile (gaseous or liquid) material. Beyond the inner planets lies the asteroid belt, a zone of dispersed rocky material without enough mass to create a planet of its own. The outer planets (Jupiter, Saturn, Uranus and Neptune) are much larger gas giants, consisting largely of light atoms and molecules (hydrogen, helium, methane, ammonia) in their gaseous or liquid form, though possibly with rocky cores. We postulate that when the sun condensed enough to start the fusion reaction that provides its energy, the early, violent solar wind drove volatiles away from the inner planets, a closer ­to ­home instance of photoevaporation. The Earth consists of three primary layers: the metallic core, ~16% of its volume; the dense rocky mantle, ~83% of its volume; and the crust, with a wide variety of rock types that constitute less than 1% of Earth volume, but more than sufficient to entirely conceal the mantle. When the Earth formed it was essentially uniform and molten. This state aided in the initial stages of differentiation by which the Earth’s layers were formed. Dense metallic liquid sank, lighter materials rose, and materials that did not want to solidify at depth rose to the top to create the beginnings of the crust. If liquids and gases at the surface were driven from the Earth early in its history, where did its current atmosphere and hydrosphere come from? One possibility is from an external source, such as comets, but most evidence points to an internal source, from volatiles expelled from volcanoes. LECTURES 2 and 3: MINERALS In a geologist’s definition, a mineral is a (i) a naturally ­occurring, (ii) inorganic substance, (iii) with a definite chemical composition or a composition that may vary only over a specified range, in which (iv) the matter is solid and crystalline, the atoms occupying a regular, repeating three ­dimensional pattern. If the same atoms were positioned in a chaotic, disorganized array, it would be a glassy substance, not a crystal. Many substances that are of interest to geologists, including synthetic gemstones, coal, petroleum, and volcanic glass, do not consist of minerals. Well ­formed crystals of a specific mineral like quartz have faces that are flat planes that always intersect at the same angle. This external regularity of crystals suggests an internal order. The atomic structure of a mineral is determined by probing the crystal with penetrating, very short ­ wavelength radiation, a method called x ­ray diffraction. A unit cell is the smallest, simplest 3 ­D piece of the three ­ dimensional atomic pattern that contains all the information necessary to con...
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This document was uploaded on 03/03/2014 for the course GEO 303K at University of Texas at Austin.

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