ARD - Absolute and Relative Dating Techniques Module Overview

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Absolute and Relative Dating Techniques

absolute and relative dating techniquesUnderstanding the history of the Earth (and by extension, the solar system) requires an ability to create a timeline or sequence of events.   In order to accomplish this goal, scientists rely on two broad types of dating techniques - those that focus on relative dating, and those that attempt to determine absolute dates.   Relative dating simply tries to determine the sequence of events - what happened first, what came next, etc. without arguing when each of these events occurred, while absolute dating attempts to estimate how long ago an event actually took place.   This module will investigate the variety of ways that scientists create both types of historical data, as well as the advantages and shortcomings of each of these dating strategies.

Essential Questions:

  • In what ways do scientists use mathematics and computational thinking to calculate the absolute age of rocks?
  • Using relative age principles, interpret a geologic cross section and describe how unconformities form.
  • How can the principle of uniformitarianism show the relationship between sedimentary rocks and their fossils to the environments in which they were formed?

Key Words:

  1. Absolute Age - the true age of a rock or fossil, absolute age tells scientists the number of years ago a rock layer formed
  2. Cross-cutting relationship -  principle that states that an intrusion or fault is younger than the rocks that it cuts through
  3. Fossils -  the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock
  4. Geologic Cross Section -  graphical representations of vertical slices through the earth used to clarify or interpret geological relationships with or without accompanying maps
  5. Geologic Time Scale -  a division of Earth's history into blocks of time distinguished by geologic and evolutionary events
  6. Index Fossil -  a fossil that is useful for dating and correlating the strata in which it is found
  7. Law of Superposition  – principle that states in a sequence of sedimentary rock layers, the oldest layer is at the bottom and the youngest layer is at the top
  8. Original Horizontality  - sedimentary layers were horizontal or lying flat at the time they were deposited
  9. Principle of Uniformitarianism -  the idea that the geologic processes that shape the land today have acted in the same way throughout Earth's history
  10. Radiometric Dating  - a method of dating specimens by determining the proportions of particular radioactive isotopes present in a sample.
  11. Relative Age -  the age of an object in comparison with the age of other objects
  12. Stratigraphic columns -  a cross section of rock showing a sequence of sedimentary rocks, with the oldest rocks on the bottom and the youngest on top
  13. Unconformity -  a boundary between rocks of very different ages. Unconformities are often marked by an erosional surface
  14. Varve -  the annual layer of sediment or sedimentary rock is called a varve, alternating light and dark bands of particles

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