Relative geologic time asks you to use very fundamental principles of geology (horizontally, superposition, cross-cutting relationships, intrusive relationships, etc.) to solve a puzzle. Because the GTM uses a symbolic way of representing the effects of geologic processes, it may initially not be clear what some of the 3D graphics mean. Here are some hints:
  1. 1.The yellow material is always the “beginning” rock layer:

  2. 2.Sedimentation is represented by the red layer. If sedimentation is the "newest" process you will see water on top. Sedimentation produces a flat upper surface - if the top of the red layer is not flat, then it has been affected by another subsequent process!

  3. 3.Erosion is represented by grooved surfaces.

  4. 4.Faulting in GTM is always normal faulting  which offsets features along a initially smooth fault plane.

  5. 5.Faulting followed by erosion will erode the fault plane as well.

  6. 6.Volcanoes are represented by cones fed by a feeder dike. If faulting occurs after the volcanoes, the fault plane  will cut across the dike

  7. 7.If erosion follows the volcanoes, the volcanic cones will be gone and only a grooved dike will be visible.  

  8. 8.If sedimentation follows the volcanoes, the volcanic cones will simply be buried without any change to their shape - these cones will only be visible in “Transparent” mode!