Materials needed


  1. Supply of Ping Pong balls.
  2. Colored Markers.




  1. Divide students into pairs or small groups. Each group has a Ping Pong ball and a marker.
  2. One student creates a depression in the ball with both thumbs. The other student marks around the top edge of the depression and then around the top of both thumbs.




  1. What shape is drawn around top of depression? This semi-circle shape represents an Island Arc formed by the subduction of ocean plates.
  2. Where is the deepest part of the depression inside or outside the Island Arc? The outline of the thumbs is the deepest part of the depression and is inside the semi-circle. This represents the location of the deepest earthquakes in a subduction zone.
  3. Students should draw a labeled picture of this activity to keep in a Tectonic Plates Clues folder.



Figure 1 Example of activity record.