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42 Cards in this Set
- Front
- Back
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What does geologic time represent? |
The entirety of Earth's history (4.5-4.6 billion years) |
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What is the geologic time scale used for? |
To sub-divide geologic history into smaller increments of time based on common events/themes |
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What data was used to construct the geologic time scale? |
The fossil record, ice ages, warming trends, volcanic/tectonic activity and radioactive decay |
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What is the fossil record? |
A record of various plants, animals, etc. that have existed on the Earth and their traces and remains that were preserved |
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What was used extensively to develop the geologic time scale? |
The fossil record |
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The fossil record: What are index/guide fossils? |
Fossils that were wide-spread geographically, but existed for a limited time period. |
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The fossil record: What is the fossil succession/Faunal succession? |
The overall assemblage of fossil changes over time. |
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The fossil record: Example of a mass extinction |
The extinction of the dinosaurs at the end of the Mesozoic |
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The fossil record: Example of Diversification of Species |
The explosion of mammal species following the extinction of the dinosaurs due to a new lack of competition |
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What are Ice Ages? |
Periods of global cooling, which bring about major climatic and ecological changes |
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What are warming trends? |
Periods of global warming, which bring about major climatic and ecological changes |
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What is volcanic/tectonic activity? |
Periods in which there is an increase in volcanic, tectonic activity, or some other process which could trigger cooling or warming trends and thus environmental changes |
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What is Radioactive Decay? |
The radioactive decay of unstable isotopes, which decays at a constant rate and can be used to determine geologic ages for rocks and minerals. |
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What are Absolute dating/ages? |
Involve the use of radioactive decay of unstable isotopes and produces an actual numerical age |
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What are Relative dating/ages? |
Involve the use of several principles to place a series of rocks and other geological features such as faults, into a sequential order from oldest to youngest |
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What are Absolute dating techniques? |
They utilize the use of unstable radioactive isotopes which decay at a constant rate. As these unstable (parent) isotopes decay, they produce more stable daughter isotopes, heat, and in some cases additional materials like alpha particles, beta particles, and electrons |
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What are Decay Processes? |
The 3 basic decay processes
*Alpha Decay *Beta Decay *Electron Capture |
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Alpha Decay |
An alpha particle is produced in addition to the daughter isotope |
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Beta Decay |
Beta particle is produced in addition to the daughter isotope |
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Electron Capture |
Electron is captured to produce the daughter isotope |
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What is half-life? |
The amount of time it takes for 50% of the parent isotope to decay and form an equal amount of the daughter isotope |
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What do half-lives represent? |
The decay rate which is constant for an individual isotope |
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How long can half-lives be? |
Short or long depending on the isotope involved |
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How do half-lives determine age? |
The number of half-lives that have elapsed can be used to determine the age of a sample by using either a decay curve or mathematical equation |
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What are the 8 relative dating techniques? |
Principle of original horizontality Principle of superposition Principle of cross-cutting relationships Principle of inclusions Index fossils Dendrochronology Unconformities Lateral tracing |
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Principle of origional horizontality |
Sedimentary rocks are deposited in horizontal layers. If they are not horizontal, something must have alter them after deposition |
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Principle of superposition |
Sedimentary rocks are progressively younger as they reach the surface. Deeper rocks are older than rocks near the surface. |
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Principle of cross-cutting relationships |
When faults and intrusions cut across other rocks they must be younger than the rocks they cut across. If a fault offsets a series of rock layers, the rock layers had to be deposited prior to the faulting. |
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Principle of inclusions |
If one rock is included/incorporated into another rocks, it must be older than the rocks that surrounds it. A rocks that was produced by a weathering is older than the new sediments that are deposited with it. |
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Dendrochronology |
The study of tree ring data from wood used during ancient times, such at an archeological or anthropological site |
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Unconformities |
These surfaces typically represent a gap or hiatus in the rock record, typically produced by erosion or non-deposition |
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Disconformity |
An unconformity that forms between parallel sedimentary rocks |
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Non conformity |
An unconformity that forms between crystalline igneous or metamorphic rocks below and younger sedimentary rocks above |
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Angular conformity |
An unconformity that forms between non parallel sedimentary rocks, ie. the rocks that are at an angle to each other |
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Lateral tracing |
Distinctive rock units can often be identified and traced from one site to another |
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K-T Mass Extinction |
Occurred at the end of the Mesozoic between the Cretaceous and Tertiary and caused the majority of dinosaur species to die off, most likely traced to an impact in the Yucatan Peninsula
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What significance does the Chicxulub Crater have? |
Crater contains shock-impact quartz and Iridium. No dinosaur fossils are found above this layer. |
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Permian Mass Extinction |
Mass extinction that occurred at the end of the Paleozoic (permian) was much larger than the extinction event that killed the dinosaurs. Corresponds with a time period in which volcanic activity was much greater than today. Volcanic activity triggered the release of greenhouse gasses that produced global warming and the reduction of oxygen gas dissolved in sea water. Anaerobic bacteria began to thrive and produced hydrogen sulfide gas, killing much of the life in the oceans. The hydrogen sulfide gas escaped to the surface and killed land-based plants and animals and then damaged the ozone layer. |
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Cenozoic Era |
Age of recent life. Quarternary period, Tertiary period. |
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Mesozoic Era |
Age of middle life. Cretaceous period, Jurassic period, Triassic period. |
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Paleozoic Era |
Age of ancient life. Permian period, Pennsylvanian period, Mississippian period, Devonian period, Silurian period, Cambrian period. |
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Precambrian |
The time between the birth of the planet and the appearance of complex forms of life were first studied. |
