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ConcepTest: Cross-Sections of Plate Boundaries

ConcepTest questions by David McConnell, David Steer, Walter Borowski, Jeffrey Dick, Annabelle Foos, Jeffrey Knott, Alvin Konigsberg, Michelle Malone, Heidi McGrew, Kathie Owens, and Stephen Van Horn
This material was originally created for Starting Point:Introductory Geology
and is replicated here as part of the SERC Pedagogic Service.

Question:

The map below shows the plate configurations along the western margin of North America. Which of the four diagrams on the right best represents a cross section through the outer layers of Earth along the line X-Y?
Pacific North American plate boundary PacificNorth American plate boundary

Student Responses:

The correct response is A.
Percentage of students choosing this answer. (% Before Discussion/% After Discussion):

a. (40%/60%)
b. (35%/40%)
c. (10%/0%)
d. (15%/0%)

in a small (< 60 students) physical geology lab section

Instructor's comments:
I asked for students to explain their reasoning. Those that answered B didn't notice or understand the divergent boundary off the coast. This question was a good way to discuss the reason for the convergent boundary off of WA coast and transform boundary of the CA coast.

If you would like to help acquire more Before and After statistics for this example, please contact the authors (see link at top of page).

References and Notes: