19 Motion at Plate Boundaries

Elizabeth Johnson

Learning Objectives

Students will be able to:

  • Interpret the type of plate boundary based upon motion shown in cross-sectional or map view.

 

Review: The Three Types of Plate Boundaries

We already investigated the topography of plate boundaries in a previous chapter: Applications: Plate Tectonics

There are three types of plate boundaries: convergent, divergent, and transform boundaries.  We can see the relative motion of these boundaries in cross-sections, or slices through Earth:

Figure 1. Divergent plate boundaries, showing plates moving away from each other. Image modified from Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research, vectorised by User:Lichtspielderivative work: Lichtspiel (Ocean-birth_hg.png) [CC BY-SA 2.5], via Wikimedia Commons.
Figure 2. Convergent plate boundaries, showing plates moving towards each other. Images compiled from https://opentextbc.ca/physicalgeology2ed/chapter/10-4-plate-plate-motions-and-plate-boundary-processes/, Steven Earle. CC BY.

 

Continental-continental conservative plate boundary opposite directions.svg
By domdomegg – Own work, CC BY 4.0, Link

Figure 3. Transform plate boundary, showing plates moving alongside each other.

 

  • At divergent boundaries, plates move away from each other.
  • At convergent boundaries, plates move towards each other.
  • At transform boundaries, plates move alongside each other.

 

We can also look at these plate boundaries in map view (looking down on the boundary from space).  It is possible to determine the type of plate boundary in map view, if the plate motions are represented by arrows.

Figure 4. Three plate boundaries in map view.

 

 

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