GLY1000Test 2 Study Guide Rheology/Deformation, Earthquakes, Interior of the Earth/Gravity and Magnetism, TectonicsSome 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 easierRheology and Deformation:-Stress: A force that produces deformation to a body. (dynes/sq. centimeter)-Formula ForceArea-Tensional stress involves forces pulling outwards -Compressional stress involves forces pushing inwards (think: compressing) -Strain: The deformation that results from stress.-Formula Δ LLo or change∈lengthoriginallength-Shear Modulus μ: (also known as Rigidity Modulus) is derived from the equation StressStrain or F / Atanθ -Bulk Modulus β: measures incompressibility, derived from the equation PH∆ V /Vo orhydrostatic pressurechange ∈volumeoriginal volumeRemember: 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 tempsGLY1000Test 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 Faultthe 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 hundredsof years until a great amount of elastic strain builds up while others produce more frequent, lessintense 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:GLY1000Test 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 InteriorComposition/Physical Characteristic of Layers of Earth: (in order from surface to core)GLY1000Test 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-Lithosphererigid, brittle, mechanical-Asthenosphereless rigid, more viscous, hotter, softens rock-Transition Zone450-700 km, seismic velocities much greater-Lower Mantlepressure very high, normal silicate phases replaced by more dense minerals-Outer Coreliquid, about 2,266 km thick, contains spinning Iron and Nickel-Inner Core5300 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: GM1 M2d2 M=mass, d=distance between humans and center of earth-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 temperaturetemp above which a material loses its permanent magnetism-magnetic inclinationangle the magnetic field lines make with the earth’s surface-magnetic declinationangle between magnetic/geographic north and south-apparent polar wanderingthe 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.GLY1000Test 2 Study Guide Rheology/Deformation, Earthquakes, Interior of the Earth/Gravity and Magnetism, Tectonics-Magnet reversals: while the geomagnetic field
View Full Document
Unlocking...