Lec 5 - Geologic Time

Lec 5 - Geologic Time - REVIEW LECTURE 5 GEOLOGIC TIME:...

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REVIEW LECTURE 5 – GEOLOGIC TIME: Superposition, Folding, Unconformities Principle of Uniformitarianism – “The present is the key to the past” The physical, chemical, biological laws that operate today have also operated in the geologic past. The oldest rocks found on Earth are 4.4 billon years old and were found in Australia. Scientists estimate that the Earth is 4.6 billion years old. Basis for relative dating : 1. Principle of ORIGINAL HORIZONTALITY – sedimentary rocks are deposited in horizontal layers. If the layers are not horizontal – then something happened after deposition 2. Principle of SUPERPOSITION – when a rock sequence is both undisturbed and deposited horizontally, the youngest rocks are found on top . This answers the question about which “way is up.” 3. Principle of CROSS-CUTTING RELATIONSHIPS a. Any igneous rock either lies on top of previously existing rock layers (extrusive igneous rock) OR cuts into previously existing rock (intrusive igneous rock). Therefore, any intrusive igneous rock formation must be
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This note was uploaded on 09/26/2011 for the course GEOL 3413 taught by Professor Hileman during the Spring '11 term at Oklahoma State.

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Lec 5 - Geologic Time - REVIEW LECTURE 5 GEOLOGIC TIME:...

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