Converging Tectonic Plates Demonstration
During this demo, participants use springs and a map of the Pacific Northwest with GPS vectors to investigate the stresses and surface expression of subduction zones, specifically the Juan de Fuca plate diving beneath the North American plate.
Skills and concepts that students must have mastered
Students should be familiar with plate subduction and convergence boundaries
How the activity is situated in the course
This demonstration can be used at any time in an earth science class, though is particularly useful when discussing plate tectonics, convergence boundaries, and the use of GPS to measure ground deformation. This demonstration is expected to take 5 - 15 minutes.
Content/concepts goals for this activity
- The Earth is not always rigid.
- The Juan de Fuca and North American plates form a subduction zone in the Pacific Northwest where the Juan de Fuca plate moves beneath the North American plate.
- The Juan de Fuca and North American plates are "locked" at the plate boundary, causing the North American plate to be pushed and compressed inland.
- The land near the coast, closest to the plate boundary, crunches the most while farther inland, the land crunches less - similar to a spring.
- Scientists monitor motion of the land with GPS.
- During a large earthquake on the subduction zone, the western edge of the North American plate will spring westward.
Higher order thinking skills goals for this activity
Other skills goals for this activity
Description and Teaching Materials
Converging Tectonic Plates Demonstration Write-up (Acrobat (PDF) 62kB Nov12 21)
Teaching Notes and Tips
A complete video of this demonstration can be found on the UNAVCO YouTube Channel.
Ask learners to summarize their observations and to sketch the maps of before convergence and after convergence of the boundary. As an extension, have learners draw a velocity vector for each dot shown on the map.
The exercise includes sample questions the learner could answer. These can be used for formative assessment of understanding or they can be graded on a simple 2-point scale:
- 2 points = correct answer with thorough supporting evidence and/or complete description
- 1 point = answer not completely correct or lacking thorough supporting evidence or description
- 0 points = incorrect answer
References and Resources
- Plate Motion Calculator (UNAVCO)
- What can GPS tell us about future earthquakes? (UNAVCO YouTube Video)