GLY1000 Test 2 Study Guide Rheology Deformation Earthquakes Interior of the Earth Gravity and Magnetism Tectonics Some things to keep in mind Mafic LOW in silica HIGHER temperature LESS viscous Felsic HIGH in silica LOWER temperature MORE viscous Water makes melting of rock easier Stress A force that produces deformation to a body dynes sq centimeter Rheology and Deformation Formula Force Area Tensional stress involves forces pulling outwards Compressional stress involves forces pushing inwards think compressing Strain The deformation that results from stress Formula L Lo or change length original length Shear Modulus also known as Rigidity Modulus is derived from the equation Stress Strain or F A tan Bulk Modulus measures incompressibility derived from the equation P H V V o or hydrostatic pressure change volume original volume Remember the HIGHER the incompressibility the HIGHER the Bulk Modulus Think of bulky items being harder to compress Factors effecting the type of strain whether solids are brittle or ductile depends on their temperature and strain rate brittle at low temps and ductile at high temps GLY1000 Test 2 Study Guide Rheology Deformation Earthquakes Interior of the Earth Gravity and Magnetism Tectonics brittle under high strain rates and ductile under low strain rates Types of Faults Reverse or thrust Fault the crust is under primary compressible stress with the following fault lines Normal Fault the crust is under primary tensional stress with the following fault lines Strike Slip Fault the crust is under primary shear stress Fault lines on surface Earthquakes To simplify what causes earthquakes Think of Earth s crust as a giant jig saw puzzle and the pieces of the puzzle representing tectonic plates The edges of these puzzle pieces represent plate boundaries These boundaries slowly move around and bump into each other When a boundary with a fault gets stuck against another boundary one keeps moving When the two slip as a result of built up elastic strain energy an earthquake forms Major hazards of earthquakes Insufficient city design of buildings and structures ground shaking can cause these to crumble Tsunamis big threats precautions could include concrete tsunami walls and alert systems Why some great faults generate earthquakes along some segments of their lengths but not along others San Andreas what can account for them Some sections that produce large scale earthquakes remain somewhat dormant over hundreds of years until a great amount of elastic strain builds up while others produce more frequent less intense earthquakes Distribution and depth Most earthquakes occur in linear belts and arcs How deep the foci are shallow up to 70 km below surface intermediate 70 300 km or deep 300 km Why they originate in lithosphere but not in the asthenosphere Lithosphere only moving brittle layer of Earth Asthenosphere is too hot therefore more mafic less rigid How earthquake depths associate with types of plate boundaries GLY1000 Test 2 Study Guide Rheology Deformation Earthquakes Interior of the Earth Gravity and Magnetism Tectonics Earthquakes vary based on what type of boundary they re formed convergent boundaries subduction and collision Collision shallow broad seismic activity Subduction more complex deeper Factors that affect the level of damage caused by an earthquake Location magnitude depth distance from the epicenter geological conditions construction Liquefication of sediments during earthquakes Liquefication process of loose soil acting like a liquid during an earthquake Landslides can occur more damage to buildings on unconsolidated sediments Signs of impending earthquakes decrease of crustal seismic velocities swelling in local volume of crustal rocks produces bulging doming ground tilting increased emission of radon from the crust changes in the water level in wells changes in the activity of geysers Magnitude amount of energy released on a numerical scale of 2 10 Difference in whole 30x Magnitude can be determined w a seismometer by measuring P and S waves P Wave Compressional shock wave that vibrates in the same direction it travels Travels faster than S Wave Velocity depends on elastic moduli and density of transmitting medium S Wave Transverse wave shear wave that vibrates perpendicular to direction it travels Velocity depends of shear modulus and density of transmitting medium The Earth s Interior Composition Physical Characteristic of Layers of Earth in order from surface to core GLY1000 Test 2 Study Guide Rheology Deformation Earthquakes Interior of the Earth Gravity and Magnetism Tectonics Crust Continental About 30 km thick felsic Oceanic About 5 7 km thick made of oceanic sediments gabbro and basalt Lithosphere rigid brittle mechanical Asthenosphere less rigid more viscous hotter softens rock Transition Zone 450 700 km seismic velocities much greater Lower Mantle pressure very high normal silicate phases replaced by more dense minerals Outer Core liquid about 2 266 km thick contains spinning Iron and Nickel Inner Core 5300 km solid very high pressure P and S wave velocities S wave velocities don t drop as rapidly as P wave velocities P waves have higher velocities than S waves think S stands for slow in this case Gravity Equation for force of gravity G M mass d distance between humans and center of earth M 1 M 2 d2 Negative gravity anomaly mass deficiency Positive gravity anomaly mass excess isostasy equilibrium that exists between parts of the earth s crust Isostatic equilibrium is the point where two weights are equal The Earth s Magnetic Field curie temperature temp above which a material loses its permanent magnetism magnetic inclination angle the magnetic field lines make with the earth s surface magnetic declination angle between magnetic geographic north and south apparent polar wandering the perceived movement of the poles in relation to the continent Origin of magnetic field dynamo effect electric currents produced by convection along with the circulation of liquid Iron and Nickel spinning in the outer core GLY1000 Test 2 Study Guide Rheology Deformation Earthquakes Interior of the Earth Gravity and Magnetism Tectonics Magnet reversals while the geomagnetic field is reversed cooling volcanic rocks reversely magnetize Once cooled the locked in magnetization of the rock preserves its history Plate Tectonics Evidence of continental drift Theory of plate tectonics Belief that super continent Pangaea once existed and the break up of this
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