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113 Cards in this Set
- Front
- Back
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What is the definition of biostratigraphy?
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correlation and assignment of relative ages of rocks by using fossil assemblages contained within them
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What is the definition of magnetostratigraphy?
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chronostratigraphic technique used to date sedimentary and volcanic successions by measuring polarity of the earths field
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What is the definition of chronostratigraphy?
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Time relations and ages of rock bodies
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What are some methods of biostratigraphy?
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Law of Faunal Succession, Concept of stages, and concepts of zones
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Who determined the law of faunal succesion?
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Cuvier and Smith in the early 1800's
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Who began using the concept of stages in biostratigraphy?
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D'Orbigny
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Who began using the concept of zones in biostratigraphy?
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Oppel
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What did William Smith do?
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Developed the law of faunal succession and created the first geological map.
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What did Georges Cuvier do?
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Similar to smith realized that rock in the paris basin varied from east to west, but fossils remained the same. So he used fossil-based correlations. Comparing living animals with fossils Cuvier helped develope paleontology and created the fundamental idea of extinction and catastrophism.
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What is the idea of stages with relation to biostratigraphy?
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Group of strata containing a unique assemblage of fossiles. The stages are name for geographic localities with good sections that bear key fossils on which the stage is based.
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What is the idea of zones in biostratigraphy?
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It is the fundamental biostratigraphic unit. It is defined as strata characterized by an overlapping range of fossils. Represents time between different species in succeeding and preceding zones. Named after particular distinct fossils (trace fossils)
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How can time be divided in biostratigraphy?
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in 3 ways:
TIME extinct present not yet evolved ROCK absent present absent |
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What are the types of zones?
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Taxon range biozone, concurrent range biozone, and the abundance biozone
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What is the tawan range biozone?
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Stratigrapic, geographic range of a a single taxon. So correlation by taxon range zone is the correlation by index fossils. It is useful if the index fossil is short lived if not one must use another type of zone.
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What is a concurrent range biozone?
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Contains overlapping part of the range of two or more taxa
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What is the abundance biozone?
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Contains great abundance of a particular taxon or group of taxa
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What controls a fossils presence?
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Evolution, extinction, reproduction patterns, movement, and barriers of distribution
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How can evolution be broken up?
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punctuated equilibrium and gradualism
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What is important to the life history of organisms with reference to the distribution of fossils?
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Reproductive strategies, movement (plankonic in marine)
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What is the idea of zones in biostratigraphy?
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It is the fundamental biostratigraphic unit. It is defined as strata characterized by an overlapping range of fossils. Represents time between different species in succeeding and preceding zones. Named after particular distinct fossils (trace fossils)
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What are barriers to distribute fossils?
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Substrates, Climate-geographic barriers, sea level/lake level, and plate tectonics.
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How can time be divided in biostratigraphy?
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in 3 ways:
TIME extinct present not yet evolved ROCK absent present absent |
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What are the types of zones?
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Taxon range biozone, concurrent range biozone, and the abundance biozone
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What is the tawan range biozone?
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Stratigrapic, geographic range of a a single taxon. So correlation by taxon range zone is the correlation by index fossils. It is useful if the index fossil is short lived if not one must use another type of zone.
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What is a concurrent range biozone?
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Contains overlapping part of the range of two or more taxa
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What is the abundance biozone?
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Contains great abundance of a particular taxon or group of taxa
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What controls a fossils presence?
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Evolution, extinction, reproduction patterns, movement, and barriers of distribution
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How can evolution be broken up?
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punctuated equilibrium and gradualism
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What is important to the life history of organisms with reference to the distribution of fossils?
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Reproductive strategies, movement (plankonic in marine)
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What are barriers to distribute fossils?
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Substrates, Climate-geographic barriers, sea level/lake level, and plate tectonics.
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What is graphic correlation and how is it used?
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It is the biostratigraphic means of correlation. It correlates 2 intervals via stratigraphic datums the 2 have in common. One can then add more sections until they have a composite standard in which composite ranges approach true ranges
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What do magnetostratigraphy use?
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It assumes earth as a dipole and uses the main component of the magnetic field to determine field lines varying by latitude.
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What is the dynamic component of magnetostratigraphy?
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Reversal of magnetic field is repetitive but not periodic.
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What should appear on the sea floor in terms of magnetostratigraphy?
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If the sea floor is spreading the rock should show symmetrical magnetic stripes moving away from the ridge.
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What are the different types of magnetic minerals?
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They are ferrimagnetic minerals: which include magnetite, hematite, and maghemite
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What is the curie point?
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Temperature below which magnetic field is locked into rocks
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What is deposition remnant magnetization?
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Minerals become aligned during depositions, they are usually fine grained sedimentation
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How does depositional remanent magnetization work?
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In water magnetic grains wobble above the magnetic field vector as they sink, once in a slurry along the bottom magnetic grains can still rotatate, when bottom grains compress magnetic grains are locked into place
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What are apparent polar wander pathways?
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Position of magnetic pole at time of deposition.
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What is magnetostratigraohy measure?
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Sample vertically through a section, they record normal-reverse intervals, and are compared to the geomagnetic timescale that is determined mainly from the ocean crust.
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What does the geomagnetic polar time scale show?
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it shows the change in the earth magnetic field over time, one finds that boundaries are sharp and instananous, exist world wide independent of facies.
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What is hiatuses and why are the important to magneticstratigraphy?
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Hiatuses means one may miss reversal of poles. It is also important to know the rough age of any given sample.
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What is geochronology?
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One uses several methods such as decay to determine absolute dates.
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What are the different systems used in radioactive decay dating?
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Uranium-238 Lead-205 with an 4.5 billion half life
Uranium-235 Lead-207 with a 704 million half life Thorium-Lead dating with a 14 billion year half life and Samrium147 Neodymium 143 with a 106 billion year half life. |
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What are two important rules to remember about radioactive decay?
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The amount of time it takes for a single nucleus to decay is random and unpredictable
The average lifetime of a sample containing mant nuclei of the same isotope can be predicted and measured |
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What are some problems and assumptions associated with radioactive dating?
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Radioactive elements find trace elements that require precise dating
Weathering, Metamorphism or other alterations can reset the clock We assume constant rate of decay, which is a valid assumption Must have right material for any given system We must assume a closed system |
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What does a concordia plot give us with regard to radioactive decay?
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it gives on the age of nuclei loss or metamorphic even, and the age of crystallization
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What is a good method of age dating?
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Zircon dating, with a half life of 4.5 billion years, and it can be zapped using an ion probe. This all assumes one has a good zircon sample.
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What are the different termination types in seismic and what do they look like?
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What does a toplap and truncation look like in seismic?
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When and where was the first seismic shot?
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in the 1920's in oklahoma
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in seismic how do you calculate depth from time and velocity?
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depth=(time/2)*velocity
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What is important to remember about seismic sections?
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They are not geologic cross sections, vertical scale is two-way travel time, reflections are not necessarily lithological boundaries
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What did Peter Vail do at exxon?
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Formalized and integrated seismic with sequence stratigraphy in 1970's used to identify and predict depositional sequences, seismic faicies, rleative changes in sea level, lithology, porosity, and fluid content
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What is the origin of sequence stratigraphy?
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Sloss noted that stratigrahic sections were divided by unconformities and the geographic terrain and conditions could be determined.
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What are the factors affecting stratigraphy?
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Sedimentation, climate, eustacy, and subsidence
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Sequence can reflect what changes in a system?
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relative sea level change, sediment supply, tectonics, and eustacy
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What does one use when determining sequence stratigraphy?
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chronostratigraphic horizons
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What are the hierarchy of units in sequence stratigraphy?
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sequence, system tracts, and parasequences
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What are the different types of systems associated with eustacy, tectonic subsidence, and relative change?
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Low Stand, Transgressive, High Stand, shelf margin tract
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What evidence do we use for sea level change?
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sedimentar or fossil evidence for shallowing or deeping. Correlation of such sequences over large areas. and istopic evidence(ie oxygen)
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What are the different rates and magnitudes if sea-level change?
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80-120 m in Late paleozoic (ice house)
125 m in Quaternary (ice house) Large magnitude but low rates in Mesozoic(green house) |
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What are the mechanism for eustatic sea level change?
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tectonoeustacy(basin volume)
Glacioeustacy(water volume) |
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What is sequence stratigraphy all about?
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its all about recognizing types of surfaces through termination types and recognizing geometry of stratal packages between those surfaces.
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What is a sequence?
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relative conformable succession of genetically related strata bounded by unconformities or their correlative conformities. (record cycle of sea level change)
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What is a sequence boundary?
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unconformitiy or correlative conformity marked by erosional truncation (shelfward) or major basinward facies shift (seaward)
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What is a parasequence?
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A relative conformable succesion of genetically related beds or bedsets bounded by marine flooding surfaces and their correlative surfaces.(internally conformable)
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What are some controls on stratal geometry?
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rates of sedimentation and accommodation.
progradation occurs when sed>acc producing a regression retrogradation sedmentation lags accommodation, producing transgression aggradation occurs when sedimentation and accomodation track one another |
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What controls accommodation?
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Accommodation is the space available for sedimentation. It is controlled by eustasy, tectonics, and climate
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What does a retrogradation look like?
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What does progradation look like?
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What does a sequence boundary look like?
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What does aggradational look like?
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What does stratal geometry look like?
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What is the maximum flooding surface?
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surface of maximum landward movement of shorline(trangressive) marked by downlap surface on seismic, deepest water facies in core, high gamma-ray in logs, boundary between TST and HST
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What is the transgressive surface?
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Initial deepening across the shelf (within sequence). Top of lowstand wedge. Marked by stratal onlap in seismic, landward shift in facies in core.
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What is a lowstand system tract?
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Deposited in basin above sequence boundary; onlaps slope
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What is the trangressive systems tract?
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deposited above transgressive surface and below MFS; onlaps shelf with retrogradational geometry
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What is the highstand systems tract?
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Deposited above MFS and below sequence boundary; downlaps and tops laps (aggradation to progradational)
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How do we recognize surfaces?
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Seismic, Outcrop, Core, and Logs
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What is the breakdown of the earths climate?
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78% nitrogen 20% oxygen, and 1% argon
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What is the structure of the atmosphere?
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Thermosphere
Mesosphere Stratosphere Troposphere Temp decreases-increases-decreases-increases |
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How much pressure does air exert?
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14.7 lbs/sq inch
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What does pressure do with altitude?
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Drops
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Amount of water vapor in air depends mostly on?
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Temperature. Warmer air holds more water vapor. Water is added by evaporation and removed by ppt.
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How much of the earths refleceted by clouds?
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30%
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What do calculations suggest about global temperature and why?
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given energy absorbed = suns energy - reflected
and energy absorbed = energy emmited The temp should be -18C |
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Why is the earths surface so warm?
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Atmosphere has greenhouse gases?
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What is the greenhouse effect?
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molecules vibrate and rotate and energy is released in the form of heat.
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Why does the earth emit in infrared?
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Blackbody radiation has a characteristic wavelengths that depends on the bodies absolute temp. Wiens law states wavelengths of radiation emitted relates to the bodies temp. So hot bodies emit radiation at shorter wavelengths.
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What does planetary balance not mean?
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it does not mean uniform radiation, the suns radiation varies by latitude with majority directed towards the equator.
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Why do we have planetary seasons?
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This is due to the 23.5 degree tilt of the earth.
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How does radiation vary?
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daily, seasonally, by latitude, and over time
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How do circulation pattern work?
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Rising air means a low pressure zone and therefor is replaced by air from side therefor driving surface winds. and vice versa with sinking air with high pressure zones.
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What is the coriolis effect?
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An apparent force on a fluid(wind or water) moving across earths surface to be deflected from its straight line path.
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What are the major climate controls?
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Solar radiation(latitude or season), circulation of atmosphere(vertical low pressure and high pressure zones and horizontal movement which accounts for coriolis effect), and heat redistribution
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What are the land and sea contrast with relation to climate?
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Land heats up more, onshore winds during day and offshore at night.
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How is the ocean mixing?
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Wind driven (shallow), density (deep), and coastal upwelling
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What is the difference in east and west coast currents?
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east coast is warm toward pole and west coast has cold water very rich in sea life.
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Where is most of the oceans volume?
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below 500-1000 m, cold dense water that contains dissolved carbon dioxide and disolved oxygen
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What are the effects of ice caps near the poles?
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since ice caps are pure water then the salinity of the surround water increases, so dense cold water sinks.
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What are climate impacts on geologic processes?
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rates of weathering, soil developement, modes of erosion/transport, and depositional enviroments. Sedimentary rocks record ancient climates.
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What controls climate over time?
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latitude, shoreline positions, geography
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What are the primary controls on climate change?
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tectonics, atmospher compostion (carbon cycle), and solar radiation changes due to earths orbit
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What does the carbon cycle determine?
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How carbon is stored on the earth in the ocean majority of it is stored deep ocean, in land majority is stored in the soils.
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What is the milankovitch theory?
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as the earth travels around the sun, cyclical variations in 3 aspect of earth sun geometry combine to produce variations in the amount of solar energy that reaches the earth.
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What is the definition of paleoclimate?
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climate prior to instrumentation
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What is the definition of proxy records?
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natural phenomena that are climate dependent. We calibrate using uniformitarianism.
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What is the key for deep time in paleoclimates?
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Sedimentary record
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What are some paleoclimate indicators?
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Litologic(coal,carbonates,evaporites with clay and sand compostions and structures like mudcracks,ice-wedges, and cross beds)
Fossils(organisms,pollen, and trace fossils) |
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What rocks can be used as proxies?
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Evaporites, coal, wind-blown sand, marine limestone, and glacial sediments
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What can isotopes be used for?
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Oxygen will give paleotemperature
Carbon determine paleoproductivity |
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What does it mean when there is more oxygen isotopes?
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Either clouds hold O18 or land. When clouds do you have ice sheets on land.
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