GEOL 101 1nd Edition Final Exam Study Guide Lectures Chapter 14 Earthquakes and the Earth s Interior Focus hypocenter depth below the surface energy released in waves Epicenter point on surface directly above surface Earthquake waves happen usually on plate boundaries or faults Rocks on both side slide past each other creating stress and friction they will bend to accommodate but eventually will snap making the wave o Seismometers Seismographs how they work record waves on paper Have weight that is freely suspended from being attached to bedrock There is a pen and a spool of paper within it and as an earthquake happens the pen and paper move with the rock making a seismogram o P waves S waves Surface waves Relative velocities Travel at different velocities The time difference is used to locate the epicenter P waves go the fastest S waves are second and L waves are the slowest Types of motion compressional shear etc P waves move in pushpull compressional S waves move up and down and L waves are complex with both up down and side to side movement Material that will transmit each P waves go through solid liquid and gases S waves go through solids and L waves cause most damage Locating earthquakes o P wave s wave travel times the greater the time difference the farther away the epicenter is o How to locate the epicenter draw circles when trying to figure out how far away the P and S waves are o Number of stations needed three stations to triangulate the epicenter More stations more accurate Measuring earthquakes o Magnitude vs intensity scales o Richter scale most common Type of scale magnitude scale Amount of energy released per 1 unit on the scale at the focus Logarithm scale that is based on amplitude of largest seismic wave o Modified Mercalli scale Type of scale intensity scale measures degrees of earth shaking at a location based on damage Usefulness vs limitations uses in area with very few seismic stations But the damages may be more severe in poor overpopulated areas with soft sediments o Moment Magnitude scale Type of scale magnitude mearuing energy How can it be derived and verified Better at gauging size of large earthquakes Can be derived mathematically from surface structure and displacement of fault and can be verified by seismograph data Earthquake destruction o Seismic vibrations Variables that affect the amount of damage to a structure depends on intensity larger magnitude releases more energy duration longer shaking makes more damage material structures are on loose sediment is less stable than bedrock design of structures Amplification of seismic waves by soft sediments soft sediments amplify waves and increase damage while bedrock does the opposite Example Mexico City 1985 sits on top of soft sol and was damaged 400 km away from epicenter magnitude was an 8 0 Liquefaction vibrations cause loose water saturated sediment to turn from stable to mobile fluid Example Loma Prieta World Series earthquake 1989 6 9 Mw epicenter along San Andres coast line o Tsunamis massive waves set in motion by seismic activity Causes Earthquakes cause oceanic crust to be displaced along a fault and trigger land slides Example Indonesia 2004 9 1 Mw waves reached over 30 feet tall flooding and claiming 200 000 lives o Landslides down dropping of land Example Madison Slide 1959 7 5 earthquake triggered very high velocity slide in Madison county o Subsidence Example Anchorage Good Friday earthquake 1964 o Fire can break cities water lines causing fires Example San Francisco earthquake 1906 7 9 along San Andres fault greatest loss of life and property due to fire Largest recorded earthquake in US history Good Friday Earthquake Alaska 1964 Largest recorded earthquake in world history Valdivia Earthquake Chile 1960 Nebraska Earthquakes o Which fault zone are they associated with The Earth s Interior o Refraction reflection of seismic waves waves travel faster with depth which is consistent under materials under pressure Cause waves to refract bend some are also reflected back to surface Compositional layering what causes it Occur during early formation Heavier elements sank in the center with lighters ones on top chemical differentiation each layer has different chemical composition o Crust average thickness of oceanic 7 10 km vs continental 35 40 km crust 3 km at seafoor spreading and 70 km in mountain ranges o Mantle 2900 km composed of periodite o Core iron rich with radius of 3486 km Physical layering what causes it Result of pressure and temperature changes from surface to core o Lithosphere makes up tectonic plates Crust uppermost mantle both ridged layers Rigid solid gooey solid or liquid o Asthenosphere weak Upper part as small amount of partial melting so it allows lithosphere to detach and move freely Rigid solid gooey solid or liquid o Mesosphere very hot Solid or liquid o Outer core Composition Iron nickel Solid or liquid liquid o Inner core Composition Iron nickel Solid or liquid Solid Mohorovi i Discontinuity The Moho o What happens to seismic waves here Increase abruptly o What is the depth 50 km in depth o What does it indicate Boundary that separates the crust from the mantle Shadow Zone the cores o What happens to s waves and p waves when you reach 105 from the epicenter They die out but P waves reappear at 140 degrees o What happens between 105 and 140 Not there o What happens past 140 P waves come back o What happens to the seismic waves that creates the shadow zone Changed velocity and angle because of the material o How do we know that the outer core is made of liquid think about s wave behaviors S waves travel only through solids so when it did not reappear it was determined that it was liquid Chapters 15 and 16 Plate Tectonics Alfred Wegener Continental Drift 1915 Pangaea o When did Pangaea exist Mesozoic 200 Ma o What were the evidences for it The continents fit together fossils were found across continents mountain ranges are across continents paleoclimates coal bed and glaciers Seafloor spreading centers mid ocean ridges provided proof for the movement of continents o When how were the ocean ridges discovered Late 1940s US navy invested a lot to build better defense but found ocean ridge systems underwater mountain ranges o What are they Tensional forces made the floor spread out creating rifts They also discovered underwater volcanoes o What are rifts Tensional forces pulling ocean crust apart o Volcanism at the mid ocean ridges locates above zones of upwelling