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22 Cards in this Set
- Front
- Back
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The absolute age of the earth is?
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4.56 Billion Years old
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Relative Dating
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Placing events in sequence based on their position in the geologic record
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Absolute Dating
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placing a specific number of years on an event or rock sample
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How do we determine Absolute Age?
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Thickness of sedimentary rocks, saltiness of the ocean, or Radioactivity
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How do we use radioactivity
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it is the most effective way to determine the absolute age. We measure the radioactive elements near the subject to determine its age
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Which Rocks can be Dated, and what is the order of likelyhood
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Most Igneous Rocks can be dated, some metamorphic, and few sedimentary rocks
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What is a geologic contact?
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where one rock touches another sharing a surface
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What are 4 ways to determine Relative Age?
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Origional Horizontality, Superposition, Lateral Continuity, Cross-Cutting Relationships
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What is Original Horizontality?
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When beds of sediments deposited in water are initially formed horizontally
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What is Superposition?
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When layers of rocks are undisturbed, the rocks are younger at the top and older at the bottom.
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What is Lateral Continuity?
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when an original horizontal layer extends laterally, until it thins at the edges
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What are Cross cutting relationships?
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a disruption in a geologic object is younger than the object its self
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What is an Unconformity?
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a surface or contact that represents a gap in the geologic record
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What are the types of Unconformities?
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Disconformity, Angular Unconformity, and Non-Conformity
(D.A.N) |
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What is Disconformity?
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an unconformity in which the contact representing the missing rock layers is paralell
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What is Angular Unconformity?
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an unconformity in which the contact separates the overlying younger layers from the eroded, tilted, or folder layers and is covered again by sedimentary rock
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What is Non-Conformity?
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is the boundary between an unlayered body of plutonic igneous or metamorphic rock and an overlying layered sequence of sedimentary rock layers.
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What is the Order of the Geologic Time scale between the 4 major eras? And what is represented in each of these eras?
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Pre Cambrian (Oldest Represents 87% of Geologic Time)
Paleozoic (Old Life, Beggining of complex life) Mesozoic (Middle Life dinosaurs abundant) Cenozoic (New life, mammals are abundant) |
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How do we remember the periods of geology?
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Quit, Telling (Cenozoic)
Crummy, Jokes, To (Mesozoic) People, Passing, Me, Down, Some, Oreo, Cookies, (Pale) Please (Pre-Cambrian) |
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What is a Mold Fossil?
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Fossil formed when acidic water dissolves a shell or bone AROUND which sand or mud has already hardened
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What is a Cast?
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Fossil formed when mold is later filled IN by mud or mineral matter
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What is an Index Fossil?
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A fossil that is common to a particular geologic time period, that is used to help date rocks of that period
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