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87 Cards in this Set
- Front
- Back
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Principle of Original Horizontality
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All Sedimentary rocks are horizontal at deposition
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Principle of superposition
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Any sedimentary layer overlaying another bed is younger.
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Principle of original continuity
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sedimentary rocks form continuous sheet at time of deposition.
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Principle of cross-cutting relationships
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feature cutting is younger than the feature being cut.
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Principle of Biotic Succession
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Animals and plants have changed since the past and the changes define specific times in the past. William "Strata" Smith.
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Index fossil
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define precise time in past
species must exist for a short time and be found over a large geographic area. |
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Unconformities
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periods of erosion: data is being removed
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angular unconformity
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contact between two sedimentary but not parallel.
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disconformity
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contact between parallel sedimentary rocks of different rock types
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nonconformity
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contact between different rocks (sed & ign) or (sed & meta)
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paraconformity
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time gap between sedimentary layers of same lithologies.
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radioactivity
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loss of particles from an atom's nucleus
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alpha emission
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type of radioactivity. loss of 2 protons and 2 neutrons
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Beta Emission
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type of radioactivity. loss of an electron from neutron in the nucleus.
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Half Life
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amount of time it takes half of the parent (beg) to decay into the daughter (end).
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Paleozoic
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oldest on geologic time scale. 540-245 Ma. trilobite. 90% died out
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Mesozoic
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middle on geologic time scale. 245-65 Ma. dinosaurs. 75% died out.
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Cenozoic
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most recent on the Geologic time scale. 65 to recent. mammals.
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Continental Drift
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Alfred Wegener. supercontinent, Pangea, existed during most of the Paleozoic. beg of Meso Pangea split into continents it is today. criticism: how did continents move?
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evidence for Continental Drift
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fit of continents(puzzle and species)
Paleoclimate Geologic structures |
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Alfred Wegener
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discovered continental drift
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Pangea
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supercontinent in Paleozoic
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Fit of continents
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Africa & S. America fit like puzzle pieces. freshwater animal (Mesosaurus) lived in Af. & S. Amer. seed fern (Glossopteris) on many continents.
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Paleoclimate evidence
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glacier climate in warm countries. coal in cold countries.
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geologic structures
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mountain belts match across oceans and so do rock types
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Paleomagnetics
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major breakthrough for continental drift. magnetism:force produced by electric current. Earth has weak mag field. as rocks form they take current Earth mag field:fossil compass.
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geomagnetic reversals
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Paleomagnetics. the Earth's magnetic field periodically changes direction & rocks take current magnetic field.
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seafloor spreading
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breakthrough for continental drift. midoceanic ridges: global oceanic belt, parallel with continental margins (coastlines), high heatflow. deep sea trenches: deep valleys on ocean floor, seismic activity very high. MORs form in crust above convection cells:regions in mantle with high heat-->they rise. magma moves sideways at top-->crust splits magma leaks into cracks and forms new seafloor. seafloor pushed under mantle and forms deep sea trenches. Harry Hess.
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Theory of Plate Tectonics
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combination of theory of continental drift and theory of seafloor spreading. Lithosphere is made up of segments called plates. these plates slip/slide over athenosphere.
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Divergent Margins(rifting or spreading centers)
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Plate edges moves away from each other
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when a spreading center develops within a continent. what will happen?
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convection forces crust upward & splits at top. crust breaks & magma leaks in & solidifies-->volcanoes.
rift valley forms:broken pieces of lithosphere slide downward into gap, rift valley continues to get wider and wider. ocean floods into rift valley: linear sea. edges move farther away: ocean |
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Convergent Margins
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Plates move together.
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volcanic arc
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ocean-continent
granite in continent is less dense than oceanic. oceanic subducts: "subduction zone". can make deep sea trenches(lowest part on Earth's surface) plate descends into mantle, melts, hot material migrates upward & can cause explosive volcanoes on continental plate. batholiths can form when magma chambers merge together. |
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island arc
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oceanic-oceanic
one plate moves beneath another and forms submarine volcanoes. |
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collision zones
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continental-continental
neither edge can subduct. forms highly deformed mountains |
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Transform Margins
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2 plates slide past one another without creating nor destroying lithosphere
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Hot Spot
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stationary pocket of hot molten material in the athenosphere. when plates move over hot spot, creates chain of islands
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parts of a fold
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axis and limb
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axis
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median plane along the crest of a structure
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limb
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side of a fold
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anticline
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older in the core, limbs dip away from the axis. Shaped like an A
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syncline
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younger at top. limbs toward the axis. Shaped like a U.
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Monocline
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step-like structure.
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Strike
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compass direction of a flat line that touches the point of intersection where the inclined surface meets the hoizontal surface.
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Dip
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the angle under the horizontal plane of intersection.
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Joints
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crack where no appreciable movement has occurred. large scale fractures indicate past stress histories of rock.
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Fault
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displacement of rock on either side of a fracture. Dip-Slip & Strike-slip.
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Dip-Slip
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vertical offset. headwall/hanging wall (top) & foot wall (bottom).
normal fault: foot ball moved up reverse fault: head wall moved up detachment fault: low angle normal fault thrust fault: low angle reverse fault |
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Strike-Slip
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horizontal offset
stand on one block & look across the fault to see what direction it is going to determine left or right. |
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Fault indicators
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offset beds, fault gouge: pulverized rock created by faulting, slickenside: polished striated surface created by fault movement.
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Orogenic Processes
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fold-and-thrust mountain ranges: form from thick, predominantly marine layers of sediment (>5,000), strata deformed by compression
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volcanic mountain ranges
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volcanic arc
island arc hot spot spreading centers fault-block mountain centers: extension of crust causes batholith to be rotated up above surface. |
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earthquakes
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a sudden motion of trembling (breakage) in the Earth caused by the abrupt release of slowly accumulated stress (force).
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seismology
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study of "shaking"
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hypocenter/focus
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point on the fault where the quake starts
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epicenter
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point of the Earth's surface directly above the focus
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shallow quake
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<70 km below the surface
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intermediate quake
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70-350 km
velocities are much slower |
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deep quake
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>350 km
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seismograph
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device for recording earthquakes
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3 parts needed for seismograph
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fixed base, inert mass, recording device
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seismogram
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record earthquake energy
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primary waves
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compressional waves, push/pull waves, fastest waves to arrive, no damage
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secondary waves
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shearing waves(like scissors), up & down/ sideways movement
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love waves
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has a horizontal motion(shear) transverse to the direction of propogation.
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rayleigh waves
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has a retrograde, elliptical motion
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intensity
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a qualitative scale that measures damages to structures
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Modified Mercalli Scale
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US & other nations. #ed I-XII. sent out to citizens affected(they rate the quake)
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magnitude scales
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scale that quantifies energy released by an earthquake.
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Richter Scale
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each higher number on the scale is an inc of 30 the energy released.
used logarithms to account for high energy released. So Cal quakes. M1 |
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Ms
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a measurement that would handle distant quakes. deep quakes do not produce good surface waves so new Mb waves
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Mb
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Gutenberg and Richter developed a scale that uses P waves. measures P waves which are not affected by focal depth.
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Moment Magnitude
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Hiroo Kanamori. Mw. accepted as most accurate measurement of earthquake. Total amount.
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2 data sets used to interpret Earth's interior
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Magnetic Field & Seismic Waves
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magnetic field
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generated by interaction of inner and outer core.
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seismic waves
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density changes affect velocity & direction of seismic waves. inc density-->inc velocity
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refracted
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bend
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reflection
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bounced
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Mohorovicic Discontinuity
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boundary between crust and mantle
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mantle
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ultramafic. peridotite & eclogite. more dense closer to the core
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Gutenberg Discontinuity
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boundary between mantle and core
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core
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boundary @ 2900 km where S waves stop & P waves velocity drops sharply.
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shadow zone
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region where no earthquake energy is detected because it has been refracted or reflected away from that area. S waves can't go through liquids.
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P wave
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exist from 103 -143 degrees from epicenter
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S wave
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exist from 103- 180 from the epicenter
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outer core
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liquid metal, Fe & Ni
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inner core
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solid, Fe crystal
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