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35 Cards in this Set
- Front
- Back
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Proposed by James Hutton (1726-1797) Physical processes that operate in the modern world also operated in the past, at roughly the same rates. “The present is the key to the past”
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Principle of Uniformitarianism:
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sediments are most commonly deposited in horizontal layers.
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Principle of original horizontality-
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Law of ______ _______: sediments will continue laterally into the subsurface
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lateral continuity
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Law of ________: materials from older layers will be included in younger layers.
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inclusions
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Law of _____-______ ______: states that if one geologic feature cuts across another, the feature that has been cut is older.
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cross-cutting relations
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An igneous intrusion “bakes” (metamorphoses) surrounding rocks, so the rock that has been baked must be older than the intrusion.
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Principle of baked contacts
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Principle of ________ _______: William Smith (1769-1839) Different species of fossil organisms appear in a definite order; once a fossil species disappears in a sequence of strata, it never reappears higher in the sequence.
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Fossil succession
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Unconformities are
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gaps in the record.
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An unconformity represents
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a period of non-deposition and possibly erosion.
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Angular Unconformity:
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Rocks below an angular unconformity were tilted or folded before the unconformity developed.
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Nonconformity: _____ rocks overlie generally much older intrusive _____ and _____ rocks.
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Sedimentary rocks overlie generally much older intrusive igneous rocks and metamorphic rocks
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Disconformities: contact representing missing ______ separates ______ layers.
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Contact representing missing strata separates parallel layers
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Correlation: is that ___ relationship between the strata at ___and the strata at ____.
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statigraphic // one locality // another |
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Isotopic dating (aka radiometric dating) is based on _____ decay of unstable _____. Technique that measures ______ elements to calculate the ______ _____ of rocks. Started in the ______.
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nuclear decay of unstable isotopes. Technique that measures radioactive elements to calculate the numerical ages of rocks. Started in the 1950s.
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238 Uranium is used to date rocks 4.5 Ga and older known as Uranium Lead Dating Technique
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Radioactive Decay
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40 K (Potassium) used to date rocks 1.3 to 4.5 Ga
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Potassium Argon Dating Technique
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Used to date rocks 100 to 40,000 years old. Most accurately done with igneous rocks and has an accuracy of + or – 2%
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Carbon 14 dating
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Dendrochronology
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tree dating using tree rings
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appearance of invertebrates with shells defines the Precambrian-Cambrian boundary
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Cambrian Explosion
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Age of the dinosaurs
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Mesozoic |
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Age of Mammals
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Cenozoic
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First Fish Appear |
Paleozoic
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First Plants Appear |
Silurian
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first amphibians
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Devonian
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First Reptiles |
Pennsylvania
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First dinosaurs |
Triassic |
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End of Cretaceous Era marks the
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extinction of dinos |
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Rocks from the Carboniferous period contain a lot of
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coal |
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It is believed the meteorite that crashed into the earth causing the dinosaur extinction impacted at the ______ near present day ______
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Yucatan Peninsula //Cancun |
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principles of statigraphy to put geologic events in order
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a. original horizontally
b. superposition c. lateral continuity d. cross cutting relationships e. floral and faunal succession |
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original horizontally |
sediments deposited in horizontal layers
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superposition |
oldest sediments on bottom and youngest on top
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lateral continuity |
a sedimentary layer continues horizontally until it tapers out
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cross-cutting relationships |
a young unit cuts across a younger unit
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floral and faunal succession
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plant and animal evolution applied via the fossil record
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