To model the first way the plates can move in relation to each other, students place the
graham crackers side by side gently on the frosting. They slide the two crackers against
each other in opposite directions, slightly bumping and scraping while sliding. Explain to
students that this is what happens when two plates slide and that this motion frequently
causes earthquakes. Define earthquakes, and inform the students that earthquakes are
frequent along the San Andreas Fault in California — a famous example of a transform
boundary. Be sure students observe that the frosting acts as a cushion but does not
come up through the plates. Have students fill in the related blocks on the worksheet,
citing earthquakes under “Effects.”