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Unformatted text preview: \ 1.17.07 Physical Geology- Deals with processes that operate at or beneath the Earth's surface. Also with the materials (rocks) on which these processes operate. What causes Earthquakes, volcanic eruptions and where? How and where are mountain ranges formed? Geologic Time--its immensity (billions of years) is difficult to grasp. The universe is 15 billion years old, our solar system is- 4.5 billion years old. Consists of sun and 9 planets. 2 groups of planets: Terrestrial : small, rocky, dense-mercury, Venus, earth, mars Jovian : large, gassy, light-Jupiter, Saturn, Uranus, Neptune Accretion : coming/sticking together. Fig. 9.3 Earth warms up rapidly due to: Accretion- collision-al heating Compression- inner layers get heated decay of radioactive materials inside earth- continues today Early earth was partially molten. Fig. 9.4 Rocks are very poor conductors of heat. Earth may have been uniform in composition inside and outside, at first, but became differentiated/ layered. Once temp is hot//high enough iron falls down to center. Falling releases energy and causes more heating. Called icon catastrophe. Big burp= water and other gasses belched out. Distances measured from surface of earth -radius= 6400 km. Based on composition: (fig 1.5) A) crust-solid rock (0-40 km depth) B) mantle- solid rock (40-2900 km depth) C) outer core-liquid iron (2900-5100 km depth) D) inner core-solid iron (5100-6400 km depth) 1.19.07 Figure 1.5 the layers of what the Earth is made out of. Based on Mechanical strength: 1. Top layer 1-100km in depth- Lithosphere cool, strong, rocky (rigid). Rocks much below melting point; contains crust and part of upper mantle. 2. Next layer 100-300 km in depth Asthenosphere- hot, weak, (ductile bends) rocks close to their melting point. Consistency is like that of tar (silly putty). 3. Mesosphere- 300-2900 km in depth hot strong rigid rocks under very high pressure not near melting. KNOW LAYERS: Chemical composition of the Earth- Top Layer (crust) is most accessible and studied. (fig. 1.7 ) Two elements (the big 2) make up 75% of total. Oxygen and Silicon (O and Si.) Oxygen is main one. These two plus another 6 make up the big 8 99% of the crust. Aluminum (Al), Iron (Fe), Magnesium (Mg), Calcium (Ca), Potassium (K) Sodium (Na). (FIGURE 1.8 know order of big 2 know names of all 8.) Contrast with the composition of the whole earth. Most abundant in order Iron, Oxygen, Silicon, Magnesium. Most of Fe in the core most of Mg in mantle. As we go into the Earths interior it gets hotter. Rate at which the temperature increases is known As we go into the Earths interior it gets hotter....
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- Spring '07