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Rock age

eq: How do I determine the age of rock layers?. Rock age. Relative age vs. Absolute age. The age of a rock COMPARED to the ages of other rocks is relative age. Absolute age is the EXACT age of rock. Finding Relative Age.

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Rock age

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  1. eq: How do I determine the age of rock layers? Rock age

  2. Relative age vs. Absolute age • The age of a rock COMPARED to the ages of other rocks is relative age. • Absolute age is the EXACT age of rock.

  3. Finding Relative Age • Principle of Original Horizontality states that layers of sedimentary rock are laid down horizontally (from left to right).

  4. Finding Relative Age • For the Law of Superposition, in horizontal layers of sedimentary rock, the OLDEST is at the bottom. Each higher layer is YOUNGER than the layers below it.

  5. Finding Relative Age • The Principle of Uniformitarianism states that “History repeats itself.” What happened in the past will continue to happen in the same way now and in the future. *This supports the Law of Superposition.

  6. Clues to finding Relative Age • An extrusion is a layer of igneous rock that forms from lava above a sedimentary rock layer. It is ALWAYSyounger than the layers below it.

  7. Clues to finding Relative Age • An intrusion is a layer of igneous rock that forms from magma cooling amongst layers of sedimentary rocks. It is ALWAYS youngerthan the layers below it and the one it cuts through (because it formed after).

  8. Clues to finding Relative Age • A fault (or break in rock) isalso younger than the rock it cuts through.

  9. Clues to finding Relative Age An unconformity (a gap in the geologic record) occurs when: • A. Deposition builds up rock layers. • B. Some layers erode away. • C. New rock layers form on top. • D. New rock meets much older rock.

  10. /\/\/ = FAULT I = INTRUSION X = EXTRUSION • Now you try this… • Make 4 comparisons for: • 2 rock layers • the intrusion • the extrusion • the fault

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