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Unformatted text preview: GEOLOGY EXAM 1 NOTES BAKSI Chapter 1 Wednesday, January 17, 2007 12:30 PM Universe= 15 Billion Years Ago Solar System=4.5 Billion Years Ago(Sun + 9 Planets) Fig 9.3 2 groups o Terrestrial: Small, rocky, dense (Mercury, Venus, Earth, Mars) o Jovian: Large, gassy, light (Jupiter, Saturn, Uranus, Neptune) Solar System formed from relatively cold material- primarily from nebula of gas and dust that undergoes accretion Gravitational Attraction- The larger a body, more dust and gas it pulls in: Accretion Fig 9.3 Most material goes to form sun, left over forms planets, comets, meteorites. Earth warms up very rapidly due to: o Accretion- collision- al heating o Compression- inner layers get heated o Decay of radioactive materials inside earth- continues today Early earth became partially molten. Caused in part by collision with Mars Sized Body; created the Moon Fig 9.2 Then started to cool down. Rocks- poor conductors of heat. Once "crust" forms, inside still remains very hot- even today Earth may have been uniform in composition inside and out, at first, but due to heating, became differentiated- layered Fig 1.5 Once temp (T) inside high enough, some iron melts and "falls" to the center; this releases energy and causes more heating. Runaway process- lots of iron melts and falls to center Fig 9.5 Iron Catastrophe This huge heating event causes "boiling off" of volatiles from inside. Water, other gases "belched" to the outside- "The Big Burp" forms early ocean and atmosphere. Fig 9.6 Both very different from what we have today. Look at layering in two different ways. Distances measured from surface of the earth radius= 6400 km Based on composition Fig 1.5 o Crust- solid rock 0-~40 km depth o Mantle- diff type of solid rock ~40-2900 km depth o Outer Core- liquid iron 2900-5100 km depth o Inner Core- solid iron 5100-6400 km depth Chapter 1/Chapter 2 Friday, January 19, 2007 12:38 PM Based on Mechanical Strength: (i)Top Layer- 0-~100 Km Depth- Lithosphere, cool, strong, rocky, (rigid). Rocks much below melting point, contains crust and part of upper mantle. (ii)Next Layer- ~100-300 Km Depth-Asthenosphere , hot, weak, ductile(bends). Rocks much closer to their melting point. Consistency like that of Tar (or silly putty) (iii)Mesosphere- ~300-2900 Km Depth-hot, strong, rigid, rocks under very high pressure- not near melting. (NOTE- NOT BE TESTED ON MESOSPHERE) Chemical Composition of Earth: Top Layer(Crust) Most accessible and studied Fig 1.7 Two Elements (The Big 2 ) Make up 75% of total....
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