GLG 201 2.16.07 - o 1. Non-deposition: no material is being...

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Geology 2.16.07 Relative time and Event Relationships Principle of uniformity o Present is key to the past Principle of Original Horizontality o Material is deposited in horizontal layers Material/rocks at large angle to horizontal must have been moved Principle of Superposition o Material/rock on top is YOUNGER than the stuff below. Principle of Cross-cutting Relationships o If one geologic feature cuts across another, the feature that has been cut is OLDER Igneous Intrusive Rocks and relationships between rocks provide information about CHANGES that have occurred at the Earth’s surface over time How much time is represented by rocks o How do we know if ALL time is represented? Missing Time Why would rocks representing a specific time be missing?
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Unformatted text preview: o 1. Non-deposition: no material is being deposited o 2. Erosion: mater is deposited and then removed. Unconformity: a place in a sequence of rocks that marks the ABSENCE of part of the rock record Significant time is NOT represented Like an incomplete calendar We WILL discuss reasons today or Monday Three Important Types of Unconformity 1. Nonconformity 2. Angular unconformity 3. Disconformity Nonconformity Sedimentary rocks overlie igneous or metamorphic rocks Usually obvious erosion surface Angular unconformity Deformed (tilted) rocks are overlain by undeformed rocks Disconformity Parallel layers of sedimentary rock with an obvious erosion surface between...
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This note was uploaded on 03/29/2008 for the course GLG 201 taught by Professor Libarkin during the Spring '07 term at Michigan State University.

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GLG 201 2.16.07 - o 1. Non-deposition: no material is being...

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