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Unformatted text preview: GEOL 1001 Jan 17, 2007 physical geology- deals with processes that oerateat or beneath the earths surface. its immensity(billions of years) is difficult to grasp. geologist stud phenomena on very different time frames a) Seconds- hours. earthquake shakes the Universe is about 15 billion years old Solar system is 4.5 billion years old Consist of sun and 9 planets circling it 2 groups of planets a) Terrestrial: small, rocky, dense-mercury Venus earth mars b) Jovian: large grassy light-Jupiter Saturn Uranus Neptune Our solar system formed from relatively cold material Formed from nebula of gas and dust that undergoes accretion. Gravitational attraction- the larger a body the more dust and gas it pulls in- accretion (fig1.3) most of the material goes to form the sun, left overs form planets, co mets, meteorites. Earth warms up very rapidly. Due to 1) accretion-collisions-al heating 2) Co mpression -inner layers getting heated 3) Decay of radio active materials inside the earth Early earth became (partially) molten. Caused (in part) by collision with mars sized body; created the moon (fig 1.5) the started to cool down. Rocks are very poor conductors of heat . Once crust forms, inside still remains very hot- even today Earth may have been uniform in composition (inside and outside) at first, but because o heating, became differentiated- layered (figure 1.5) Once temperature (T) inside high enough, some iron melts and "falls" into the center this released energy and causes runaway process-lost of iron and falls into the center (fig 1.6) called the iron catastrophe This huge heating event causes "boiling off" of volatiles from the inside. Water other gasses "belched" to the outside- "the bifburp" forms early ocean and atmosphere (fig 9.6) Both very deferent from that we have today. Look at layering in 2 deferent ways. Distances measured from Based on composition fig 1.6 a) Crust solid rock (0-~40 km depth) b) mantel-(different type of solid rock (~40-2900 KM depth) c) Outer core - liquid iron (2900-5100 KM depth) d) Inner core- solid iron (5100 - 6900 km depth) January 19, 2007 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 mantel. (ii) next layer (~100-300 Km depth) asthenosphere , hot, weak (ductile- bends. Rocks close to their melting point. Consistency like that or tar (iii) Mesosphere(~300-2900 Km depth) hot, strong, rigid, rocks under very high pressure not near melting Chemical composition of earth Top layer ( crust ) most accessible and studied (Fig. 1.7) 2 elements ( the big 2 ) make up 75% of total In order: Oxygen (0) and silicon (Si ) These two with six other elements ( the big 8) make up 99% of the crust....
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This note was uploaded on 04/28/2008 for the course GEOL 1001 taught by Professor Baksi during the Spring '07 term at LSU.
- Spring '07