Notes for Test 1 - Geology 1000 Geologic time's immensity(billions of years is difficult to grasp Geologists study phenomena on very different time

Notes for Test 1 - Geology 1000 Geologic time's...

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Geology 1000 1/16/08 * Geologic time’s immensity (billions of years) is difficult to grasp * Geologists study phenomena on very different time frames (very short to very long) o Seconds-hours earthquake shakes the ground, a volcano spews out lava or ash o Hundreds of years noticeable erosion by rivers and at shoreline o Millions of years notable changes in life forms – evolution o Tens of million to a billion years mountain ranges are lifted up and then eroded away * The universe is about 15 billions years old (~15 B.Y. old) * Our solar system is about 4.5 billion years old (4,500,000,000) * Our solar system consists of the sun and nine planets circling it (FIG 9.3) * Two groups of planets: o The terrestrial planets or inner planets are small rocky and dense; (mercury Venus earth mars) o The jovian planets or outer/giant planets are large grassy, and light (Jupiter, Saturn, uranus, Neptune) – no more Pluto * Our solar system formed from relatively cold material. o It’s formed from a nebula of gas and dust that undergoes accretion. * Gravitational attraction – the larger a body, the more dust and gas it pulls in – accretion (FIG 9.2) * Most of material goes to form the sun, left overs form planets, comets, and meteorites. * The earth warms up very rapidly due to: o Accretion – collisional heating; still going on today. o Compression – inner layers get heated o Decay of radioactive materials inside the earth. This continues today * Early earth became (partially) molten. o Caused (in part) by earth’s collision with mars sized body; created the moon (FIG 9.4) o The earth then started to cool down. * Rocks are very poor conductors of heat. o Once “crust” forms, inside still remains very hot (example: earth still hot on inside even today.) * Earth may have been uniform in composition (inside and outside), at first, but because of heating, became differentiated – layered (FIG 1.5)
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* Once the temperature (T) inside is high enough, some iron melts and (b/c heavy) “falls” to the center; this releases energy and causes more heating. * Runaway process – lots of iron melts and falls to the center (FIG 9.5) o Called the iron catastrophe * This huge heating event causes the “boiling off” of volatiles from the inside. Water and other gases, “belched” to the outside – sometimes referred to as “the big burp” * The belched out material formed the early ocean and atmosphere (FIG 9.6) both of which are very different than it is today. * Look at layering in two different ways. o Distances measured from the surface of the earth – radius = 6400 Km (might be rounded off on test perfect example of MC question – loves to ask about numbers) * Based on composition (FIG1.50 o Crust – outermost surface; solid rock (0 – ~40 Km depth) o Mantle – also solid rock but different type of solid rock than the crust.(~40 – 2900 Km depth) o Outer core – liquid iron (2900-5100 Km depth) o Inner core – solid iron (5100-6400 Km depth) * Based on mechanical strength (the way an engineer would look at it) o Figure not in book o Top layer – lithosphere (0 - ~100 Km depth) – cool, strong, rocky (rigid); the
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