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Details Title: Dynamic Earth Description: history of the earth Total Flash Cards: 137 Created: 03/26/2007 19:57:27	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term Impact Metamorphism Definition -meteorite impats -one killed the dinosaurs -generate heat and impact Term Contact Metamorphism Definition -hot magma chamber -high temperature -low pressure Term Fault Zone Metamorphism Definition -rocks slide across each other -cold rocks-fault breccia (broken) -hot rocks- flow to make mylonite Term Hydrothermal Metamorphism Definition along mid-ocean ridges Term Regional Metamorphism Definition -continent-continent collision -cold near surface, hot deeper down -low temp/low pressure -high temp/high pressure Term Subduction Zone Metamorphism Definition -low temp/high pressure -slab is cold, takes a while to heat up Term Law of Superposition Definition -sedimentary rocks deposited younger over older Term Law of Original Horizonality Definition sediments deposited in horizontal beds Term Law of Cross-Cutting Relations Definition -younger features transect older ones -light-colored granitic dike cuts older, banded metamorphic rock Term Inclusions (Relative Age Dating) Definition -Older material encolosed within younger igneous, sedimentary, or metamorphic Term Angular Uncomformities Uncomformities (Relative Age Dating) Definition -sedimentary rock over tilted/folded/eroded strata (sedimentary rock) Term Disconformity Uncomformities (Relative Age Dating) Definition -sedimentary rock over emergence and erosion (sedimentary rock) Term Noncomformity Uncomformities (Relative Age Dating) Definition -sedimentary rock over eroded igneous rock (had intruded sedimentary rock) Term Fossil Succession Definition -gives definate interval of geologic time -fossils appear in geologic record in a definite order -based on succession of fossils found in vertical sequences of sedimentary rocks Term Dendrochronology (Tree-Ring dating) Absolute dates Definition measurement of annual ring widths at tree heights Term isotopes Definition -different number of neutrons -frequently used in radiometric dating Term Alpha Decay (Radioactive Decay) Definition -alpha particle emission -lower atomic number and atomic mass -lose an atom Term Beta decay (Radioactive Decay) Definition -beta (electron) emission -higher atomic number -same atomic mass -neutron transforms into electron Term Electron Capture (Radioactive Decay) Definition -electron capture -lower atomic number -same atomic mass -electron into neutron Term Radiometric dating Definition constant rate-> half-life Term Radiometric Dating of Rocks conditions Definition -CLOSED SYSTEM (no parent or daughter leaves the rock) -different teperatures Term Igneous Radiometric Date Meaning Definition -time since crystallization from magma Term Metamorphic Radiometric Date Meaning Definition time since metamorphism or recrystallization Term Sedimentary Radiomentry Date Meaning Definition not closed (water in it) age of clasts Term Marine Magnetic Anomalies Definition -magenetic reversals of seafloor spreading -calibrated by radiometrically dated lavas on land Term Acasta Gneisses(Canada) Definition -oldest rocks -4030 million years old Term Archaean Period Definition -3.8 to 2.5 million years ago -reducing atmosphere-little oxygen, -toxic to most current life -continental plates began to form -stromatolites abundant Term Hamelin pool stromatolites Definition -oldest organisms on earth -fossils 3.5 billion years ago -formed by single-cell organism: cyanobacteria Term Banded Iron Formations Definition -2.5-1.8 billion years ago -oxygen (waste product of plants) banded with abundant dissolved iron to yield minerals like magnetite and hematite -amount of oxygen locked up in banded iron beds-20x volume of oxygen in atmosphere today -important source of iron ore Term Proterozoic Era Definition -2.5 billion to 543 million years ago -stable continents appear and acrete -first abundant fossils of living organisms (bacteria and archaenas) Term Prokaryotes vs. eukaryotes Definition -pro-dna organized in single chromosome, no nucleus, no mitosis -euk-dna organized in multiple chromosomes inside a nucleus, mitotic division Term Ediacaran fauna Definition -late proterozoic era fossil -found on underside of course sandstone/mudstone- suggests a rapid burial -worldwide presence -not found after onslought of mineralized organisms in Cambrian period Term Snowball Earth Definition -time when Earth must have been covered by a sheet of ice -rapid greenhouse warming from carbon dioxide took Earth out of icy tomb -repeated cycle -abundant co2 held in limestones -led to proliferation of animals Term Paleozoic Definition Age of Invertebrates, Fish, Amphibians Term Mesozoic Definition Age of Reptiles Term Cenozoic Definition Age of Mammals, humans develop Term Deformation Definition -general term for changes in volume or shape of rock masses in response to applied forces -caused mainly by gravity Term Stress Definition -CAUSE of deformation -force applied to volumes of rock Term Strain Definition EFFECT of deformation resulting from applied stresses Term Uniform Stresses Definition -same in all directions -simply pressure Term Differential Stresses Definition vary with direction Term Hydrostatic Stress (type of Uniform Stress) Definition like on the bottom of a swimming pool Term Lithostatic stress (type of Uniform STress) Definition "felt" by rocks deep in the earth from overburden and surrounding rocks Term Normal Stress (type of Differential Stress) Definition directed perpendicular to surfaces Term Shear Stress (type of Differential Stress) Definition directed parallel to surfaces, causing sliding Term Compressional Stress (type of Differential Stress) Definition directed inward, leads to shortening of rock Term Tensional Stress (type of Differential Stress Definition directed outward and can lead to stretching of rock Term types of changes from STRAIN Definition -length changes -volume changes -angular changes: between lines; surfaces sliding past one another Term Strength Definition -resistance to deformation -function of pressure and depth- the deeper in the Earth, the stronger the rocks Term Elastic Deformation Definition completely and instantly recoverable Term Brittle Deformation Definition -creates sharp discontinuities -when rocks pushed beyond elastic limit (ie earthquakes) Term Ductile (Plastic) Deformation Definition -continuous deformation -begins at critical strength:YIELD STRENGTH -strength of ductile material governed by composition, temp, rate of deformation -strength lower for greater T or lower strain Term Active Areas Definition -where deformations take place on Earth -marked by earthquakes and surface deformation -plate boundaries: ridges, subduction zones, and transfrom faults where plates pull apart, converge and slide past another can result in extreme thinning or thickening of the crust Term Strike to define a plane in space -to describe faults and folds Definition compass direction in horizontal plane Term Dip to define a plane in space -to describe faults and folds Definition -inclination of plane normal to strike in the vertical plane -max inclination of the plane Term Joints (example of Crustal Deformation) Definition -cracks/fractures in rock with little/no visible displacement -common-exploited by weathering -commonly in parallel arrays or networks -(alligned squares) Term Faults (example of Crustal Deformation) Definition -fractures with obvious displacement -common-shallow crustal deformation -classified according to direction of displacement (and strain) -(shifted/displaced squares) Term Divergence (example of Crustal Deformation) Definition -vertical compression from gravity results in horizontal extension -example of divergent boundary-oceanic ridges -oceanic crust made at the ridge -lithosphere thickens and subsides as it cools Term What happens with a normal fault? Definition -before- nice horizontal layers -small offset- hanging wall drops down relative to footwall -large offset- active fault, hanging wall sliding downwards -erosion- fault line scarp Term Convergence (example of Crustal Deformation) Definition -horizontal compression -results in horizontal shortening -examples: -Thurst Fault: hanging wall moves UP relative to foot wall -older rocks move over younger rocks Term Formation of Himalayas Definition collision of India and Asia Term Surface features along a strike-slip fault Definition -rocks move past each other horizontally -stand on one side of fault surface, see where the other side moves to determine which type of lateral strike-slip fault it is -drainage offets -linear valley along fault -active and inactive fault traces Term Folds (example of Crustal Deformation) Definition -tilted and bent rock layers -caused by layer-parallel shortening -common-deeper level crustal deformation -classified by shape/geometry Term anticline (type of fold) Definition 2 sandstones incline away from each other Term syncline (type of fold) Definition -2 sandstones folding the same direction together -big "U" shape Term Dome Definition -N-S and E-W folding -circular area where strata pushed up relative to what's around it -hot targets for oil/gas -exposed by erosion- younger rocks on outside, bottom Term Basin Definition -N-S and E-W folding -rocks in center pushed down relative to what's around them -Older rocks on the outside, top Term Earthquake causes Definition -weak ones from volcanoes -strong- motion along faults, disconnect between rocks on either side of the fault, motions occur and release energy Term Elastic Rebound Theory (Earthquakes) Definition -Earthquake- elastic rebound of previously stored elastic strain energy in the rocks on either side of the fault -energy released is based on how much slick there is, how much rocks aredeformed, over how much area the fault moved Term p-waves (generated by earthquake) (body wave-travel through earth) Definition -compressional waves -horizontal pressure -~6km/s FASTER than S waves -SLOWER in liquids than in solids Term s-waves (generated by earthquake) (body wave-travel through earth) Definition -shear waves -diagonal pressure -3.5 km/s -slower than P waves -can ONLY travel through solid Term Raleigh waves (generated by earthquake) (surface wave) Definition like ocean waves Term love waves (generated by earthquake) (surface wave) Definition horizontal "shimmy" Term seismograph record Definition -P-waves arrive first (travel faster) -then S-waves -then surface waves Term one unique epicenter Definition -3 seismic stations -triangulation Term Intensity Mercalli scale Definition -meaure of the degree of earthquake shaking at a given locale -based on the amount of damage -scale: I-XII Term Richter Magnitude Scale Definition -Estimates the amount of energy released at the source of the earthquake -large eq: 9 -based on amplitude of the largest seismic wave recorded (p or s) -RMS of 2 is 10 times greater than RMS of 1 Term Calculating RMS Definition -log(amplitude) + (distance correction) distance correction is time difference between P and S wave arrival Term First Motion of an earthquake versus an atomic bomb Definition -distinct quadrants of push or pull versus all regions experiencing an initial push away from epicenter Term large earthquakes to fewer occur on... Definition -subduction zones (Alaska, Japan) -collision zones (Himalayas by India/Asia) -(both on convergent plate boundaries) -strike-slip plate boundaries on land (SF) -divergent plate boundaries (East African Rift) Term the most subduction occurs in Definition the Pacific Basin Term liquefaction Definition -from EQ shaking -caused large slope failure -cracks develop in crust Term Tsunami Definition -Earthquake waves in the sea -low amplitude (increases rapidly as seafloor shallows and speed and wavelength decrease) -long wavelength Term Earthquake prediction short-term (hours, days, weeks) Definition -based on precursor changes -uplift/subsidence of land surface periods of renewed/reduced minor seismicity -changes in gasses emitted from wells -abnormal animal behavior Term long term earthquake prediction (years, decades, centuries) Definition -based on probabilities -risk assessment maps based on historical data -seismic "gaps" :buildup of strain along plate boundary Term Seismology (geophysics-indirect investigations) Definition tells: -earthquake: location, strength, physical properties, movements -seismic refraction -seismic reflection Term magnetism (geophysics-indirect investigations) Definition -tells core dynamics, paleomagnetics (plate motions, reversals, etc) -mass flow Term heat flow (geophysics-indirect investigations) Definition tells convection/conduction, lithosphere thickness Term gravity (geophysics-indirect investigations) Definition density distributions near surface Term seismic refraction Seismology (geophysics-indirect investigations) Definition velocity, physical properties, layer thinknesses Term seismic reflection Seismology (geophysics-indirect investigations) Definition -internal gemoetry -waves bouncing off earth -mapping the subsurface (under ocean or inside the earth) Term Seismic Tomography Seismology (geophysics-indirect investigations) Definition MRI of the Earth Term velocity of compressional waves (p-waves) Definition higher velocity in higher density Term refraction Snell's Law Definition -bending-path bends away from normal to interface with increasing density (and velocity) -travel more where you can travel quickly so biggest angle in highest density increase velocity with increase depth- waves move faster inside Earth Term liquid outer core proved by: Definition -P and S wave shadow zone -P waves refracted off liquid and placed constraints on radius of liquid core -S waves ended at liquid Term Lehmann Discontinuity Definition seperation between liquid outer core and and solid inner core Term Moho Definition -seismic discontinuity of increasing P wave velocity with depth -boundary between crust and uppermost mantle (within lithosphere) Term Oceanic Crust Definition -thin (5-7 km) -dense (basaltic) -mostly young (<200 my old) Term Continental Crust Definition -thick (20-70 km) -less dense (granitic) -mostly very old (<4500 my old) Term Lithosphere Definition -thermal boundary layer -includes crust and part of upper mantle -thickness depends on temp (thin where hot and young) Term Asthenosphere Definition -hot, weak part of upper mantle -solid, but weak relative to lithosphere -NOT molten, may have melt in it Term Mesosphere Definition -strong lower part of mantle -solid like lithosphere -650-2800 depth Term Conduction Definition -without any transfer of mass from radioactive decay in Earth's interior (near surface in granitic material) -higher in young, thin lithosphere and areas of active magmatism Term Convection Definition -heat because movement of mass/water -movement of magma from mantle to surface -seafloor spreading (formation/recycling of plates) hydrothermal circulation (black smoker, geysers, etc.) Term important mechanism of cooling the Earth Definition generation of new oceanic lithosphere and recycling by plate tectonics- large scale convection of the planet Term conductive cooling of lithosphere causes Definition -lithosphere-asthenosphere boundary move down at rate proportional to: 1/(age of lithosphere)^2 Term Earth's magnetic field Definition function of matter and motion in the Earth's magnetic outer core Term Magnetic Reversals Definition show age of strips of oceanic crust worldwide Term Earth's gravity field g= Definition G(m1 x m2)/r^2 -m1=measuring device -m2=mass between device and center of Earth Term Gravity Anomoly Definition -negative=mass deficiency -positive=mass excess -show how actual gravity field differs from gravity of uniform/featureless Earth Term Satellite Altimetry Definition -determine bathymetry based upon slight changes in elevation of sea surface from greater gravitational attraction of large rock masses on sea floor (volcanoes) Term to learn topography of seafloor Definition -echo-sounding -swath mapping -satellite altimetry Term to learn geology of ocean floor Definition -side-scan sonar (reflectivity of sound signal) -ROVs (remotely operated vehicles) -Alvin (submersible) -Ocean drilling program Term Passive continental margin Definition -margin (where continental crust transitions into oceanic crust) created by spreading at mid-ocean ridge -WEST coast of South America Term Active continental margin Definition -margin (where continental crust transitions into oceanic crust) adjacent to a subduction zone (or strike-slip boundary) -contains oceanic trench -EAST coast of US Term Continental shelf on Passive continental margin Definition -submerged extension of CONTINENT -nearly horizontal -thick -(during Ice Age, was exposed) Term continental slope on Passive continental margin Definition -seaward edge shelf -steeper -boundary between continental/oceanic crust Term continental rise on Passive continental margin Definition -more gradual slope -very wide (merges into abyssal plain) -thick with sediments from continental slope -turbidity currents make deep sea fans Term deepest place on Earth Definition -deep ocean trenches -~11 km below sea level Term terrigenous on ocean basin floor Definition -derived from land-mineral grains from continental rocks Term biogenic on ocean basin floor Definition derived from organisms- marine animal shells, organisms Term precipitates on ocean basin floor Definition derived from water- minerals crystallize out of water Term mid-ocean ridge Definition may occupy as much as 1/3 of ocean basin Term hotspots Definition long-lived, large volcanic features that are randomly distributed through the ocean basins (and on land) Term seamounts Definition -smaller volcanoes that erupt commonly near the ridge axis -generally, do not rise to sea surface Term Coral Reefs and Atolls Definition marine structures composed mainly of coral (some live but mostly dead skeleton) and some algae and sediment Term Coral Reef Definition -colonies of coral generally near the shore -require warm temperature, clear sunlit water, and nutrients from ocean water Term Atoll Definition -circular coral structure with an interior lagoon -can be >1000 m thick Term Mountain Belts Definition -area of high elevation -belt of HIGHLY DEFORMED rocks resulting from contractional thickening and uplift of the crust -thickening and uplift expose deep level metamorphic and igneous rocks Term Andean type of Orogenic/Mountain Belt Definition -magmatic arcs above subduction zones -accreted terrains "smeared" onto them during subduction -Foreland basins of sedimentary rocks Term Collisional Type of Orogenic/Mountain Belt Definition collided continental margins-at least one was a subduction zone (possibly both) suture zone marks seam where 2 continents welded together remnants of Andean type typically found Term Continental shield Definition collage of old continental fragments and orogenic belts old "cratons" are rifted and surrounded by somewhat younger orogenic belts Term Wilson Cycle Major Earth Process Definition oceans open and close -rifting and continental margin development -seafloor spreading -subduction -collision -continued convergence -new cycle... Term tectonic extension Definition horizontal stretching, crust/lithosphere thinning, subsidence, sedimentation (burial) *good sedimentary record, but deep rocks not exposed Term tectonic extraction Definition horizontal shortening, uplift, crust/lithosphere thickening, erosion (exhumation) *sedimentary record deposite far away, surface material removed and deep level rocks exposed Term miogecline Definition rifted continental margin once a rift and spreading center, not a plane interior Term Suture Zone Definition marks the site of a former oceanic tract