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FINAL STUDY GUIDE GEO (got 93% on the test)

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Louisiana State University
GEOL 1001

FINAL STUDY GUIDEEXAM 1The science of geologyGeology is the science that pursues an understanding of planet EarthPhysical geology examines earth materials and seeks to understand the many processes that operate on our planetHistorical geology seeks an understanding of the origin of earth and its development through timeGeology people and the environmentMany important relationships exist between people and the natural environmentProblems and issues addressed by geology includeoNatural hazards resources world population growth and environmental issuesGeologic TimeThe magnitude of geologic timeInvolves vast times millions or billions of yearsAn appreciation for the magnitude of geologic time is important because many processes are very gradualThe science of geologySome historical notes about geologyThe nature of earth has been a focus of study for centuriesCatastrophism huge earth changing events The earth doesnt change unless a huge catastrophe occursUniformitarianism the physical chemical and biological laws that operate today have operated throughout the geological pastPhotosThe rocks at the bottom of the Grand Canyon are 1720 billion years ago The most recent layer of sediment is about 250 million years old The explosive impact of a meteorite created this 12 km wide crater in just a few secondsThe nature of scientific inquiryScience assumes the natural world is consistent and predictableThe goal of science is to discover patterns in nature and use the knowledge to make predictionsScientists collect data through observation and measurements How or why things happen are explained usingoHypothesis a tentative or untested explanationoTheory a welltested and widely accepted view that the scientific community agrees best explains certain observable factsThere is no fixed path The scientific method keeps moving forwardA view of earthEarth is a planet that is small and selfcontainedEarths four spheres areoHydrosphereoAtmosphereoBiosphereoGeosphereEarth as a systemWhat is a system oAny size group of interacting parts that from a complex wholeoOpen vs closed systemsCycles in the earth systemoHydrologic cycleoRock cycleInterface is a common boundary where different parts of a system come in contact and interactThe earth system is powered by the sun that drives external processes in the followingoAtmosphereoHydrosphereoAt earths surfaceThe earth system is also powered by earths interiorTemperatures within the earthTemperatures increase with depth in the earth Variation of T with depth defines the geothermal gradient or geothermEarly Evolution of EarthOrigin of planet of earthoEarth and other planets formed at essentially the same timeoNebular hypothesisSolar system evolved from an enormous rotating cloud called the solar nebulaComposed of hydrogen and heliumNebula began to contract about 5 billion years agoAssumes a flat disk shape with the protosun pre sun at the centerInner planted begin to form from metallic and rocky substancesLarger outer planets began forming form fragments of ices H2O CO2 and othersFormation of earths layered structureoMetals sank to the centeroMolten rock rose to produce a primitive crustoChemical segregation established the three basic divisions of earths interioroA primitive atmosphere evolved from gases in earths interiorEarths internal structureLayers defined by compositionoCrustoMantleoCoreLayers defined by physical propertiesoLithosphereoAsthenosphereoMesosphereoInner and outer coreDiagramLess dense continental crust floats on denser mantleContinental crust is less dense than oceanic crustOceanic crust has a higher density heavier than continental crustMantle has the most densityThe face of earthEarths surfaceoContinentsoOceansContinentsoMountain beltsMost prominent feature of continentsoThe stable interiorAlso called a craton composed of shields and stable platformsOcean basinsoOceanic ridge systemMost prominent topographic feature on earthComposed of igneous rock that has been fractured and upliftedRocks and the Rock CycleBasic Rock typesoIgneous rockCooling and solidification or magma molten rockExamples include granite and basaltoSedimentary rockAccumulate in layers at earths surfaceSediments are derived from weathering of preexisting rocksExamples include sandstone and limestoneoMetamorphic rocksFormed by changing preexisting igneous sedimentary or other metamorphic rocksDriving forces are heat and pressureExamples include gneiss and marbleThe rock cycle one of earths subsystemsoThe loop that involves the processes by which one rock changes to anotheroIllustrates the various processes and paths as Earth materials change both on the surface and inside the earthPlate tectonics A scientific revolution unfoldsContinental Drift An idea before its timeoAlfred WegenerFirst proposed continental drift hypothesis in 1915Published The Origin of Continents an OceansoContinental drift hypothesisThe supercontinent called Pangaea began breaking apart about 200 million years agoContinents drifted to present positionsEvidence used in support of continental drift hypothesisFit of the continentsFossil evidenceoAlligator fossils were found in rocks of the same age in South America and AfricaRock type and structural similaritiesPaleoclimatic evidenceoPaleo cold Existence of continental glaciers on the bottoms of the southern continentsMatching mountain rangesPolar Wandering Paths for Eurasia and North AmericaNo one believed the man who first came up with this theory because he couldnt explain why the continents have drifted apartThis was not proven true until scientists figured out how to determine where the magnetic north pole wasA scientific revolution beginsDuring the 1950s and 1960s technological strides permitted extensive mapping of the ocean floorThe seafloor spreading hypothesis was proposed by Harry Hess in the early 1960sHe concluded that the seafloor was spreading away from the large mountain rangesGeomagnetic reversaloSwitching of N and S polesoFound in oceanic crustPlate tectonics The new paradigmEarths major platesoKnown as the lithosphere consists of uppermost mantle and overlying crustoOverlies a weaker region in the mantle called the AsthenosphereoPlates move relative to each other at a very slow but continuous rateAbout 5 centimeters 2 inches per yearCooler denser slabs of oceanic lithosphere descend into the mantlePlate boundariesoDivergent plate boundaries constructive marginsoConvergent plate boundaries destructive marginsoTransform fault boundaries conservative marginsRates and history of plate motionMagnetic anomaliesSeafloor areas of high and low magnetic valuesEarths magnetic fieldOriginates in liquid outer coreLine of force exit and enter earth at magnetic poles offset from geographic polesPresent day normal polarity Lines of force exit earth at magnetic south reenter at magnetic northPaleomagnetism and reversalsRocks records magnetic field at time of crystallization
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