Mid-term Review - Geology 240Lxg Notes LECTURE 1 Geology...

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Geology 240Lxg Notes 28/08/2009 18:35:00 LECTURE 1 - 1/15/08 Geology 240Lxg “Earthquakes (a.k.a. Geophysics)” Professor Sammis Syllabus on blackboard.usc.edu Where do EQ occur, and why? plate boundaries What is an EQ? faults, slips, epicenters, hypocenters etc. What are EQ waves? Using waves to locate EQs Using waves to measure earth structure Reflection and projection EQ forecasting and engineering Zoning Where to build structures etc. Sciences Pure Sciences Physics (motion, matter and response to forces, energy) Chemistry (nature of matter) Applied Sciences Biological Sciences Descriptive : Classification Biochemistry Biophysics (radiation, reaction of cellular structures) Earth Sciences Classification Geochemistry Geophysics History of Earth Sciences Geological time
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Relative time vs. absolute time Age of Earth = 4.6 Billion Years…dated by meteorites Age of Universe = 13.6 Billion Years…dated by the rate at which the universe is expanding…by reversing time, you end up at the Big Bang (a.k.a. 13.6 BY) Where EQ occur and why: o Occur in belts, plate boundaries o What is an EQ?—EQ waves, using waves to locate EQ and measure Earth’s structure—layered/cross mantel Reflection/refraction o EQ hazard mitigation “prediction” forecasting, why it is such a difficult issue to overcome EQ engineering, make buildings safer EQ zoning Sciences: o Pure sciences o Physics—motion of matter in response to forces, energy o Chemistry: nature of matter Applied Sciences o Biological sciences: descriptive: classification o Earth sciences: classification o Biochemistry: interaction with radiation o *Geophysics: EQ fall into this category History: geological time: relative time vs. absolute time o If you look at a cross section of the earth, layers are visible to the eye, the layers at the bottom are the oldest, layers at the top are the youngest o Unstable isotopes o Half life decay is an exponential decay curve The constant rate is Independent of temperature or pressure described by half life How to find the age of a rock since it cooled from the time it was melted o MassU over Mass Pb=time Age of the Earth: 4.6 billion years (dating meteorites, stony meteorites) o Most meteorites are collected in Antarctica Type II: carbonaceous chondrites
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The entire solar system is the same age, created 4.6 billion years ago o The oldest rocks in ocean basins are .2 billion years old (200 MY) 13.6 billion years ago—Big bang o The Universe is now expanding at a measureable rate, if you go back in time you get a big bang and it all comes together which was 13.6 billion years ago, we have no idea what happened previously Age of the earth=4.6 billion years dated by meteorites Universe=13.6 billion dated by expanding rate LECTURE 2 - 1/17/08 Continents move about 1cm a year o They don’t move continuously, they move in jerks and those are EQ o
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