Final Exam Study Guide (Version 2)
Final Exam Study Guide (Version 2) GEOL 306
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This 8 page Study Guide was uploaded by Maddie Evans on Monday December 7, 2015. The Study Guide belongs to GEOL 306 at University of Oregon taught by Dr. Bindeman in Summer 2015. Since its upload, it has received 65 views. For similar materials see Volcanoes and Earthquakes in Geology at University of Oregon.
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Date Created: 12/07/15
Geology that Stud Guide quotDoes not mimic all textbook notes or Photos from Lecture slides read both for more information Study Guide Info Discussed in Review Lecture General Informa oh VVV V V VVVV V V V VVV VVVV V VV Younger plates are always more buoyant than older plates Plates that are subducting quickly will have larger earthquakes than those that are subducting slowly Large earthquakes occur every 250600 years the last one was 309 years ago and ruptured an entire subduction zone Iron can be found in the lower mantle core Lithosphere contains peridotite Asthenosphere is made up primarily of plastic Surface is never created only recycled surface can be subducted and melt away but be created again later San Andreas is a transform fault Magma squeezes through surface lithosphere Crust is 765km deep lithosphere 200 km deep upper mantle 600km deep lower mantle 650 km deep Convergent boundaries when plates smashing against eachother Himalayas an example as plates squished against each other and raised Divergent boundaries when plates moving away from each other and allowing magma to seep up between plates Transform boundaries when sliding past each other hand model demonstrated in class The stronger the offset the stronger the earthquake Roughly 150 hot spots around the world Subduction melting is called ux melting as it releases water Primary wave P wave comes moments before an earthquake and will be the first indication of a quake Secondary wave S wave occurs after the primary wave and before the large magnitude shaking Greatest shaking felt over soft mud moderate shaking felt over sand and gravel little shaking felt on bedrock Richter scale is labeled logarithmically Quake waves concave up because can t go through dense core Tsunami waves will always raise substantially at shallow water Basall c Volcanoes gt Shield volcanoes gentler slopes low viscosity lava little pyroclastic material large volumes of gasses Ex Mauna Loa Iceland s volcanoes gt Stratovolcanoes steeper slopes moderate viscosity high H20 levels half pyroclastic gt Cinder Cones mostly pyroclastic single event eruptions Scales to Measure Ea r hqua lees gt Mercalli Scale Used in 1902 how people feel largerlonger shaking would be deemed a large earthquake gt Richter Scale Began in 1935 Instrumental how the seismograph feels and length of P and S waves gt Moment and Seismic Energy Quantitative but perameters uncertain Tsunami Generating Even s gt Subduction plate can cause pressure and releasing will generate earthquake and tsunami Calderas or sectors collapse and cause waves Landslides or ice falls into ocean Volcanic eruptions usually don t cause tsunamis but sector collapses can Mt St Helens VVV Review Information for 1 quot Half of T erm Theory of Plate Tectonics gt Earthquakes tend to occur at plate boundaries where plates are shifting and creating tension and friction on one another they can be divergent or transforming gt Volcanoes tend to occur at plate margins where heat is excessively produced gt Plates are always moving hence the almost constant earthquake activity gt The evolution of ora and fauna could be due to the plates moving as they grow but separate from each other causing changes in species that resemble one another at plate boundaries Three Theories of Tectonics gt Continental drift hypothesis 19121960 s gt Fixed land masses before 1960 s gt Modern plate tectonics 1960current 1912 Continental Drift Theory gt Matching Continental Plate Boundaries if one was to cut up continents and paste them together as puzzle pieces they would match up almost perfectly aside from slight erosion gt Similarities of oras and faunas animal and plant species are similar at continental boundaries see puzzle analogy above gt Alternative Explanations 0 Ice or wood rafting animals plants could have been transferred from one land to another by raft 0 Land bridges small portions of land may have been connected to continents and allowing ora and fauna to relocate Ocean Floor Discoveries gt Central rift valleys indicating tension between plates gt Central rift valley having high heat ow and having volcanism gt Deep ocean trenches are usually the deepest parts of the ocean and are usually long and narrow gt Unable to determine ocean ooding older than 200 million years by drilling and dredging Paleomagnetism gt Magnetic field changes with time gt Magnetic pole and rotational pole are averaged to change over thousands of years gt Magnetic reversal happens roughly every 5 to 1 million years Switching North and South poles Polar quotWanderingquot gt From 1950 to 1960 gt The magnetic field in young lavas in Eurasia pointed toward our North pole but in older lavas would point to other locations or South pole gt This caused poles to quotwanderquot or assume continental movement Spreading and Subduction gt Explained by Henry Hess from Princeton gt When oceanic crust is slowly pulled apart from the middle magma and molten rock seeps in between the cracks and fractures to create the new oceanic crust Convection cells move downward and bring the plate down and the sea oor is gradually deepened Ocean oor always young because always renewed DivergentExtensional spreading ConvergentCompressional Subduction Slip Transform VVVV V Geometry and Kinematics of Plate Motion gt Triple junctions are where convergent divergent or transform plate boundaries meet in various combinations to accommodate movements on a sphere s surface o The Earth could not only be made up of one type of faulting has to adjust to the crust and area gt The Atlantic Ocean is a largely passive continental margin gt The Pacific Ocean including the Ring of Fire is an active continental margin gt The Indian Ocean is both passive and active Subduction Zones gt The density of the subducting plate will always be greater than the underlying plate 0 Asthenosphere 325 gcm3 0 Continental Lithosphere 310 gcm3 0 Old Oceanic Lithosphere 328 gcm3 0 Young Oceanic Lithosphere 326 gcm3 gt Continental Crust is rarely subducted Transform Plate Boundaries No new crust is created Usually occurring in ocean basins The act of sliding back and forth with no volcanism Creates the strongest earthquakes with friction San Andreas Fault 0 Has power to offset river deltas o In the future Baja California would be located where Alaska currently sits VVVVV Plate Tectonics and Volcanism gt Melting of the mantle 0 Partial melting usually occurs Melting in midocean ridges and hotspots common and aids in spreading Peridotie is the most abundant rock on Earth and most other planets Makes up the mantle and it s core Not seen often on surface or upper crust VVVV Density and Viscosity gt Oil is less dense than water and will oat gt Oil is more viscous than water and doesn t ow as easily Thermal Expansion gt When something is heated it expands and becomes less dense and less viscous Hot Spots gt Credited with ability to form oceanic islands gt Appear to move but always staying still and moving plates slide over and form islands Hawaiian Islands gt Leaving tracks on moving plates V VVVV Can produce medium to high volumes of basaltic magma Large volumes in the first 1 2 million years but gets weaker with younger islands Granite Sand Sandstone Quartzite Types of rocks 0 Igneous granite basalt gabbro o Sedimentary sandstones limestone o Metamorphic schist gneiss Si02 silica concentration in rock and magma determines the chemical and physical properties of rocks color mineral composition density viscosity etc Peridotite makes up most of the mantle Basalt makes up most of the oceanic crust Andesite makes up most of the continental margins Rhyolite and granite make up most of the continents Igneous Rocks gt VVV V Volcanic erupted on the surface 0 Containing glass and vesicles 0 Usually finegrained o Effusive lava o Pyroclastic volcanic ash scoria pumice bombs Plutonic cooled and crystallized at depth 0 Contains larger crystals Magma is melted crystals and gas Lava is magma that has lost its gas Igneous rock is solid that was made from cooled and fullycrystallized plutonic or partially crystallized volcanic magma Volcanism and Plate Tectonics VV V V VV 5 types of volcanism Midocean ridges basaltic almost completely underwater less viscous shield volcanoes quite effusive eruptions Hot spots when under continents form huge calderas and rhyolitic eruptions Subduction zones above water level viscous explosive pyroclastic eruptions and form island arcs Intraplate volcanism mostly basalt more explosive Magmatism of continental collision zones mostly granite little basalt little volcanism Textbook Mates Chapter 2 V VVV VVVV V V VV Distinction between mantle and crust based on rock composition Lithosphere the stiff and rigid outer rind of Earth containing tectonic plates Asthenosphere has inner hotter and more easily deformed rock Elevation difference between continental and oceanic crusts is explained by isostacy buoyancy Earth s plates move up to 11 cm per year Eruptions occurring daily along oceanic ridge systems Spreading centers in continents pull apart at much slower rates and don t usually form plate boundaries High Cascades volcanoes are an example of Convergent boundaries subduction where the oceanic crust is diving underneath the continental crust San Andreas Fault has moved California at least 350 kilometers so far Transform faults generate the most earthquake and all have potential to be catastrophic 1 to 2 dozen rigid lithosphere plates make up the outer 60 to 200 kilometers of Earth Continenttocontinent collision is where the tallest mountains are formed and largest earthquakes Chapter 6 V VVVV V V VVVVV VV Melting temperature controlling when a rock becomes magma Magma chambers are large masses of molten magma that rise through Earth s crust and usually erupt to form volcanoes Rhyolitic magma ows extremely thick and stiff Fissure is when a crack opens in the oor and erupts a large basalt ow Pahoehoe lava is very easy owing Aa lava is blocky and hard owing Volcanic Explosivity Index VEI quantifies the eruption size volume and violence Phreatic eruptions are violent steamdriven explosions generated by vaporization of shallow water in the ground Strombolian eruption is fed by magma that interacts with groundwater or seawater Vulcanian eruptions include ash falls that dominate Mauna Loa is Hawaii s largest volcano that has erupted 33 times since 1843 Etna s eruptions feature occasional violent episodes Cinder cones are basalt but characterized by small size low viscosity steep sides and moderate volatile content Stratovolcanoes have moderate volume and size moderate viscosity and slope and moderate volatile content gt gt The tectonic environment dictates the volcano distribution type composition and behavior Volcanoes that are not near plate boundaries are generally situated over hotspots Review Information for 2quot Hatf of T arm Muck of information is EM text or EM Photos of Lecture slides on Canvas Waves and Rays V VVVV Sound waves are compression of the air Water waves are compression and surface waves Wave through solids are a combination of compression shear and surface Re ected waves and rays can calculate the velocity of the material at a certain depth as well as the depth of that particular layer Earth imaging mentioned above is the main tool for seismic tomography Seismogram gt VVV First seismograph was in 1887 when a pen was suspended over a piece of paper attached to the ground and distance travelled was recorded Earthquake can only be heard in aftershocks or after quake has occurred S waves can t propagate through liquids Natural and artificial earthquakes help image and map the world along with it s crust groundwater sea oor etc ShortTerm Earthquake Predictions VVVVV Minor earthquakes precede larger ones Look for changes in the ground motion Groundwater levels will be rapidly uctuating Gas radon levels Early warning systems implemented in cell phones LongTerm Earthquake Predictions gt gt gt gt Checking recurrence intervals at certain areas or fault lines Earthquake hazards map and familiarity with dangerous areas Seismic gaps Migrating earthquakes EarthquakeSafe Structures VVVVV Reinforced concrete Wood framing No bricks stone or mud too vulnerable Framed property will be damaged but with no collapse Steel exible frames and safe distances between highrise buildings in cities Meteorites and Comets VVVVV Meteorites comes from asteroid belts 515 kms Comets come from the Oort belt 6070 kms Comets can lose all water and become meteorites Meteorites on Earth collected from the Moon Mars and Venus Idea that the Moon was formed from a highimpact meteorite that split the Earth s mantle into pieces that created the orbiting planet Tsunami General Information VVVVVV 51 meter not high in open water but high on shallow beaches Wavelength is 300 kilometers Very gentle slopes When nearing shore will gain elevation but lose speed Several arrivals arriving 1530 minutes apart Most dangerous in bays and harbors Tohoku Earthquake and Tsunami VVVVVVV March 11 2011 Magnitude 90 lasted 6 minutes One of top 5 earthquakes in the world and largest in Japan Wave 40 meter high 16000 did 125000 building destroyed 300 billion damages worst ever for natural disaster Due to subduction megathrust most common for earthquakes
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