GEOL 101 1nd EditionFinal Exam Study Guide LecturesChapter 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 waveo Seismometers/Seismographs – how they work record waves on paper. Haveweight 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 push-pull (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 earthquakeso 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 earthquakeso Magnitude vs. intensity scaleso 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 waveo 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 destructiono 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 lineo 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 Interioro 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 perioditeo Core iron rich with radius of 3486 km. - Physical layering – what causes it? Result of pressure and temperature changes from surface to coreo 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? liquido Inner core Composition? Iron-nickel  Solid or liquid? Solid- Mohorovičić Discontinuity (The Moho)o What happens to seismic waves here? Increase abruptly o What is the depth? 50 km in deptho What does it indicate? Boundary that separates the crust from the mantle. - Shadow Zone & the coreso What happens to s-waves and p-waves when you reach 105º from the epicenter? They die out but P-waves reappear at 140 degreeso What happens between 105º and 140º? Not thereo What happens past 140º? 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-wavebehaviors) 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) - Pangaeao When did Pangaea exist? Mesozoic (200 Ma) o What were the evidences for it? The continents fit together, fossils werefound across continents, mountain ranges are across continents, paleo-climates (coal bed and glaciers)- Seafloor spreading centers/mid-ocean ridges provided proof for the movement of continentso When & how were the ocean ridges discovered? Late 1940s, US navy