Term
Be able to reconstruct the geologic history of an area from a cross-section (using the principles of relative dating). In other words, know how to use the rules for relative dating. |
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Definition
1. The Law of Original Horizontality - most rocks laid down flat, and tilted only later during geologic events 2. The Law of Superposition - oldest rocks are on the bottom 3. Law of Lateral Continuity -most rock beds don't end suddenly when originally laid down 4. Law of Cross-cutting relationships - A rock being cut by another rock or feature is older than that rock or feature 5. Law of Inclusions -If rock A includes pieces of rock B, then rock B is older than rock A 6. The Law of Fossil Succession - Fossil assemblages change in an ordered succession through time. |
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Term
Know the various forms of “up indicators”. |
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Definition
graded bedding fossils, such as tree stumps, animal burrows, root traces channel fill cross bedding mud cracks raindrop impressions infilled voids flute and scraape casts and molds vesicles at the top of a lava flow |
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Term
What is the definition of “fossil” and “trace fossil”? |
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Definition
fossil - a remnant, impression, or trace of an animal or plant of past geological ages that has been preserved in the earth's crust trace fossil - when the organism itself is not preserved but only evidence of its existence (dinosaur tracks, worm burrows, coprolite) |
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Term
Who was the person who developed the principle of fossil succession, where did he work, what did he do, and when did he work? |
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Definition
William Smith Surveyor Early 1800s English |
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Term
What are index fossils and ecological indicator fossils? |
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Definition
- can tell you what kind of an environment that rocks were formed in - a good ecological indicator exists through a long period of geologic history, and has a limited tolerance for variation in their environment (must live in a specific type of environment) |
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Term
| Know the definition of an unconformity, and the four types (your book only has three). |
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Definition
a break in the stratigraphic rock record - missing time angular unconformity disconformity nonconformity paraconformity |
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Term
Be able to reproduce the Geologic Time Scale from memory. |
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Definition
Cenozoic Mesozoic Paleozoic |
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Term
Know the three types of radioactive emission. |
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Definition
Alpha 4p+ 2e- Beta 1e- Gamma - |
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Term
| Understand the concept of a half-life (t1/2), and how it can be used to find the age of a rock/mineral. Be able to find the age of a rock given: parent to daughter ratio, and the half-life (t1/2) of the radioactive element in question. |
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Definition
100% - 0 50% - 1 25% - 2 12.5% - 3 6.25% - 4 3.125% - 5 |
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Term
| What assumptions are made in this “absolute dating” method? |
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Definition
1. rock or mineral system is closed 2. Initial ratio of parent to daughter must be determined 3. half life must be constant through time 4. measurements of parent and daughter must be accurate (need minimum amount) 5. A realistic value must be applied to daughter amount (can't be too small) |
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Term
What rock types are most useful for this method? |
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Definition
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Term
What other physical aspect of a rock can be used to constrain its age. |
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Definition
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Term
| How old are the oldest rocks and minerals in the world, and where do they come from? |
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Definition
oldest rock - Acasta - 4.055 billion years - Canada Mineral Zircon crystal - 4.4 Billion - Austrailia |
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Term
Where were the oldest fossils found, and how old are they? |
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Definition
acasta gneiss from the canadian shield green land |
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