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93 Cards in this Set
- Front
- Back
Uniformiterianism (Actualism)
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"the same natural laws that exist today and govern the earth has governed the earth forever.
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Types of dating
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Relative & Absolute
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Relative Dating
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Original Horizontality, Superposition, Lateral Continuity, Cross cutting relationships
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Original Horizontality principle
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when beds are forming they are originally deposited horizontally
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Superposition principle
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older rocks on the bottom, younger rocks on top
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Lateral continuity principle
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normally bed extends laterally until in pinches out to nothing ex. Mt St Helens ash. If it ends in a blunt/cut off end then something must have happened to it.
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Cross cutting relationships principle
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a geological feature that cuts across rock is younger that the rock it cuts across – a dike is younger than the layers that it cuts across – the fault is younger than the rock it cut through
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Inclusions principle
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fragments that are included in the host rock are older than the host rock - ex. Xenoliths
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Unconformities
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"a surface where there is a gap in the geologic record “Time is missing”
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Angular unconformities
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"beds below the unconformity are not parallel to the beds above the
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Non Conformity
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sediments are deposited on intrusive igneous or metamorphic rocks
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Disconformity
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rock layers above & below the unconformity are all parallel. – one way to tell if time is missing – if one layer that has fossils is next to a layer that also has fossils of different time period.
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Correlation
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determining the time equivalency of rock units using Physical continuity, Rock types, Fossils
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Absolute dating
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Isotopic and Radioactive decay
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Isotopic Dating
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Parent, Daughter, half life
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Radioactive Decay
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Alpha Decay, Beta Decay, electron capture
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Geological Structure
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Stress & Strain
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Stress
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force acting on a rock
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Strain
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change in shape and or size of a rock as a result of stress
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Types of Stress
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Compression, tensional stress, shear
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Types of deformation
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Elastic, Ductile, Brittle Deformation
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Compression Stress
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pushing together - stress results in shortening strain
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Tensional Stress
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pulling apart – results in extensional (lengthening) strain
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Shear force Stress
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parallel forces pushing in opposite direction
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Elastic deformation
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Rocks return to their original shape or dimension after stress is released
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Ductile deformation
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fold or bend – rocks that are like playdough – it will not go back to its original shape
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Brittle Deformation
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breaks rocks
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Folds
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bend in rock units – results from ductile deformation
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Types of folds
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Anticline, Syncline, Plunging, Structural dome, Structural basin
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Anticline fold
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Upward arching fold
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Syncline fold
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trough shaped – downward arching
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Plunging fold
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axis is not horizontal
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Structural dome fold
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all beds dip away from a central point
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Structural basin fold
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all beds are toward a central point (salad bowl)
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Shapes of folds
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Open Folds, Isoclinal folds, Overturned folds, Recumbent folds
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Open folds
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less intense stress
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Isoclinal folds
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intense stress – ie: Christmas ribbon candy
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Overturned Fold
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shear stress or unequal compressive stress
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Recumbent Fold
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formed in the center of mountain ranges where there is a lot of crustal shortening (Himalayas)
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Parts of a fold
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Limbs, Axis, Axial plane
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Fractures
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Break in a rock, result of brittle deformation
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Kinds of fractures
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Joint, Fault
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Parts of a fault
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Fault Plane, Fault Trace, Hanging wall, Foot wall
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Best places to observe faults
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Roadcut, quarries, sea cliffs
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Types of faults
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Dip Slip Fault, Strike Slip Fault
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Types of Dip Slip Faults
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Normal, Reverse, Thrust
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Earthquakes occur when
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the stress exceeds rupture strength of rock, Stress exceed friction between the rocks on opposite sides of fault, mass changes
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Parts of an Earthquake
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Focus, Epicenter, fault trace
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Focus
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Point on a fault where the first movements take place
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Epicenter
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Point on earth's surface directly above the fault
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Seismology
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Study of Earthquake waves
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Types of earthquake waves
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Body waves - p & s waves Surface waves - Raleigh & love waves
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P Wave
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Compressional waves - push pull movement - travels through solids & liquids
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S Wave
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Shear waves - side to side motion - only travels through solids
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Raleigh waves
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Surface wave - up & down movement - like being on a ship - SS Raleigh
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Love waves
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Surface wave - side to side movement - causes the most damage
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Seismograph
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Instrument used to measure earthquake waves - has to be anchored in bedrock
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Inertia
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An object at rest tends to stay at rest
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Which wave is faster
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P wave is faster that S wave
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Equation determine distance earthquake
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ts-tp=d(1/rs-1/rp)
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Number of recording Seismograph
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Need minimum of 3 recording seismographs to determine epicenter of earthquake
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Measuring wave
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Can only measure distance not direction of waves
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Earthquake Size
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Intensity & Magnitude
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Intensity of Earthquake
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What you feel
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Magnitude of Earthquake
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measure of total energy released in a earthquake
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How do you measure Magnitude
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Richter Scale, Moment Magnitude
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Earthquake Damage
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Ground shaking, Tsunami, Liquification, Landslides
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Predicting Earthquakes
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Microseisms, Water well levels, animal behavior, Paleoseismology
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Earthquake Size
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Intensity & Magnitude
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Intensity of Earthquake
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What you feel
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Magnitude of Earthquake
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measure of total energy released in a earthquake
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How do you measure Magnitude
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Richter Scale, Moment Magnitude
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Earthquake Damage
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Ground shaking, Tsunami, Liquification, Landslides
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Predicting Earthquakes
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Microseisms, Water well levels, animal behavior, Paleoseismology
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Way to tell what’s under surface of earth
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Earthquake waves, Volcanoes Kinder light, Physics Laws
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Classical Layers of earth defined by
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defined by the composition of layers
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Classical Layers of earth
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Crust, Mantle, Core
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Oceanic Crust
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thin, dense, Rock - Mafic, basalt/gabbro, Minerals – amphiboles, plagioclase, olivenes, pyroxene
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Continental Crust
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thick, Less dense than oceanic crust, Rock – Felsic, grantite/rhyolite, Minerals – quartz, k Spar, micas
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Mantle
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denser, Rock – ultramafic, peridotite, Minerals – olivine – pyroxene, garnet
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Core
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Very dense, mostly iron (Fe) – a little O, S, Si
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MoHo
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boundary between crust & mantle where seismic waves speed up.
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ULVZ
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Ultra Low Velocity Zone – Seismic waves slow down
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Geophysical Layers - defined by
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Defined by the state that the matter is in
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Geophysical Layers
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Lithosphere, Asthenosphere, Mesophere,Outer Core, Inner Core
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Lithosphere
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Crust and the upper mantle, Solid
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Asthenosphere
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Extends from the base of the lithosphere to depth of 660 km, Plastic – flows very slowly
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Mesophere
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Solid – due to pressure
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Outer Core
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Liquid - because it is liquid we have a magnetic field
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Inner Core
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Solid – because of pressure
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Isostacy
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Balance of equilibrium of blocks of crust, the crust is very thick under mountains, Crust will rebound with pressure off
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Magnetic Field
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Region of magnetic force that surrounds the earth, Generated by convection currents in the outer core, Polar reversals
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Paleomagnetism
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Study of ancient magnetic fields, Curie Point - magnets lose magnetism - 580, When cooled - magnet points in direction of pole
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