1. Relative Dating

2. Relative Dating is one of the methods that geologists use to help tell geologic time. It can NOT tell us exactly how old something is, but… It can tell us which is older and which is younger (in a given sample)

3. The First “Law” of Relative Dating Uniformitarianism: This basically states that the processes that are occurring today are very similar to the processes that have been occurring since Earth formed (or at least shortly after the Earth formed). Weathering/Erosion Weathering/Erosion Deposit of Sediments Deposit of Sediments Gravity Gravity Etc… Etc…

4. The Second “Law” of Relative Dating Originally Horizontal or Superposition: Simply states that the rocks are going to be deposited in horizontal layers, with the oldest ones at the bottom, and the youngest ones at the top. Again, Gravity doing its thing Again, Gravity doing its thing

5. The Third “Law” of Relative Dating Cross-Cutting Relationships: Igneous rocks (those that form from the cooling of magma), that intrude into, or move through layers of sedimentary rocks (rocks that form from the deposit of sediments), are younger than the rocks they are cutting through

6. The Fourth “Law” of Relative Dating Unconformity: A “missing” section or layer of rocks (usually caused by erosion of a layer, or layers, with new/additional deposits on top).

7. Using The “Laws” of Relative Dating

8. Let’s Start With An Easy One…

9. A Little Tougher… E—oldest: superposition, on bottom C—superposition B—superposition A—superposition D—crosscutting relationship and inclusions F—youngest: crosscutting Relationships E C B A D F