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35 Cards in this Set

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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”
Principle of Uniformitarianism:
sediments are most commonly deposited in horizontal layers.
Principle of original horizontality-
Law of ______ _______: sediments will continue laterally into the subsurface
lateral continuity
Law of ________: materials from older layers will be included in younger layers.
Law of _____-______ ______: states that if one geologic feature cuts across another, the feature that has been cut is older.
cross-cutting relations
An igneous intrusion “bakes” (metamorphoses) surrounding rocks, so the rock that has been baked must be older than the intrusion.
Principle of baked contacts
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.
Fossil succession
Unconformities are
gaps in the record.
An unconformity represents
a period of non-deposition and possibly erosion.
Angular Unconformity:
Rocks below an angular unconformity were tilted or folded before the unconformity developed.
Nonconformity: _____ rocks overlie generally much older intrusive _____ and _____ rocks.
Sedimentary rocks overlie generally much older intrusive igneous rocks and metamorphic rocks
Disconformities: contact representing missing ______ separates ______ layers.
Contact representing missing strata separates parallel layers
Correlation: is that ___ relationship between the strata at ___and the strata at ____.

statigraphic // one locality // another

Isotopic dating (aka radiometric dating) is based on _____ decay of unstable _____. Technique that measures ______ elements to calculate the ______ _____ of rocks. Started in the ______.
nuclear decay of unstable isotopes. Technique that measures radioactive elements to calculate the numerical ages of rocks. Started in the 1950s.
238 Uranium is used to date rocks 4.5 Ga and older known as Uranium Lead Dating Technique
Radioactive Decay
40 K (Potassium) used to date rocks 1.3 to 4.5 Ga
Potassium Argon Dating Technique
Used to date rocks 100 to 40,000 years old. Most accurately done with igneous rocks and has an accuracy of + or – 2%
Carbon 14 dating
tree dating using tree rings
appearance of invertebrates with shells defines the Precambrian-Cambrian boundary
Cambrian Explosion
Age of the dinosaurs


Age of Mammals

First Fish Appear


First Plants Appear

first amphibians

First Reptiles


First dinosaurs


End of Cretaceous Era marks the

extinction of dinos

Rocks from the Carboniferous period contain a lot of


It is believed the meteorite that crashed into the earth causing the dinosaur extinction impacted at the ______ near present day ______

Yucatan Peninsula //Cancun

principles of statigraphy to put geologic events in order
a. original horizontally
b. superposition
c. lateral continuity
d. cross cutting relationships
e. floral and faunal succession

original horizontally

sediments deposited in horizontal layers


oldest sediments on bottom and youngest on top

lateral continuity

a sedimentary layer continues horizontally until it tapers out

cross-cutting relationships

a young unit cuts across a younger unit
floral and faunal succession
plant and animal evolution applied via the fossil record