USING DATA FOR MODERN PLATE BOUNDARIES (DISCOVERING PLATE BOUNDARIES, SEISVOLE) TO HELP STUDENTS EVALUATE GEOLOGIC SURVEY DATA, RECOGNIZE AND LOCATE ANCIENT PLATE BOUNDARIES IN THE CONTINENTAL INTERIOR

Students (K-16) often find it difficult to grasp the idea that Minnesota, currently near the center of the American Continent and far from any active plate boundary, actually preserves the record of multiple ancient plate boundaries. The exercise developed to address this issue uses Discovering Plate Boundaries (DPB) resources (www.geophysics.rice.edu/plateboundary), the the SeisVolE program (www.iris.edu/manuals/manuals.htm), and simple geologic, magnetic, and gravity maps produced by the Minnesota Geological Survey (www.geo.umn.edu/mgs/glgmaps.html).

A general knowledge of plate tectonics is assumed or built at the outset, using the SeisVolE and DPB materials. The students are then divided into six groups: strike-slip/transform boundaries; divergent boundaries (continental rift, mid-ocean ridge), and convergent boundaries (oceanic arcs, continental arcs, continental collision zones). Each group examines two active examples of their assigned boundary type. Available data includes: rock (and sediment) type, volcanic and earthquake data, topography, relative age, structural characteristics, as well as magnetic and gravity signatures. They generate a summary cross section and simple cartoon map that depict these features, and share their results with the group. Spontaneous or guided group discussion touches on the potential fate of material at each plate boundary type, preservation potential, metamorphism, and structural disruption.

The students are divided into new groups that contain a representative from each plate boundary group. The new groups are presented with geologic, gravity and magnetic maps of Minnesota, and a map that outlines the three ‘packets’ that show Archean and Proterozoic terranes in the Upper Midwest. Students then use their knowledge and data to interpret the probable type (or mixture of types) of plate boundary recorded by each packet.

The exercise was initially designed for a teacher workshop held at the Science Museum of Minnesota. It has subsequently been adapted for use in Introductory Geology labs, courses for pre-service teachers, and Middle- and High-School classrooms. This exercise is eminently transferable to other locations, including currently active boundaries that preserve a record of deposition at a passive margin or continental interior.