Relative Dating Listing

Looking at the cross-sections of rock formations, we can determine the relative ages of the layers and features in the formation. The study of strata is called stratigraphy. The table below lists five events that can occur in a rock forming environment:

  1. Sedimentation
    1. Description:
      1. Nicholas Steno's (1638-1686) laws.
      2. Sediments are laid down in horizontal layers - Steno's Principle of Original Horizontality.
      3. Younger layers are above older - Steno's Principle of Superposition.
    2. Tectonic location / process: Subsidence due to tectonic processes or changes in sea level.
  2. Deformation
    1. Description: Layers of rock are folded and distorted.
    2. Tectonic location / process: Usually caused by mountain building at convergence boundaries.
  3. Intrusions
    1. Description: Magma can cut across existing rock formations. Such a cross-cutting event must be younger than the formations it crosses.
    2. Tectonic location / process: Results from hot spot magma intrusions or magma intrusions due to melting at convergence boundaries.
  4. Erosion
    1. Description: Gaps in the geologic record caused by erosion of rock are called unconformities.
    2. Tectonic location / process: Results from uplift at convergence boundaries.
  5. Faulting
    1. Description: Another cross-cutting event.
    2. Tectonic location / process: Found at most tectonic boundaries.