Using Students' Sketches to Recognize Alternative Conceptions About Plate Tectonics Persisting From Prior Instruction

ABSTRACT

Should instructors assume that students possess conceptual knowledge of plate tectonics when they reach a second college geoscience course? Five cohorts in a historical geology course over 5 y—a total of 149 students—completed an in-class assignment in which they drew sketches of plate boundaries with required annotations. Analysis of the sketches revealed that most students lack an explanatory mental model that links the locations of earthquakes, volcanoes, and magma generation to plate-boundary processes and hold a pervasive alternative conception of Earth's interior structure that does not distinguish between compositional and rheological boundaries. Students who drew sketches that illustrated the most alternative conceptions also scored lower on a beginning-of-the-course administration of the Geoscience Concept Inventory, showing that conceptual understanding of plate tectonics correlates with overall conceptual geoscience knowledge obtained during previous course experiences. In addition, students tracking to the historical geology course via an introductory physical geology course showed stronger conceptual understanding of plate tectonics than those choosing an Earth-system science prerequisite, with those students previously enrolled in both courses illustrating the fewest alternative conceptions.

Key words: :

• plate tectonics
• misconceptions

FIGURE 1: Student sketches illustrating the alternative conceptions listed in Table I. Authors of sketches A and C followed a suggested legend, whereby asterisks represent earthquake locations and balloons represent the generation and rise of magma. Sketches A–C illustrate the general alternative conception (G, see Table 1 for abbreviations) that depicts the crust as being separate from the lithosphere. Sketch A also illustrates alternative conceptions about earthquake locations (Con1) and magma generation (Con2) at convergent boundaries. Sketch B also reflects Con1 and Con2 and places volcanoes in the trench at the plate boundary, rather than on the over-riding plate (Con3). Sketch C illustrates earthquakes deep within the lithosphere and on either side of, rather than at, the divergent boundary (Div1) and shows magma originating below the asthenosphere (Div2). Sketch D depicts a trough rather than a ridge at the divergent boundary (Div4) and shows magma rising from deep in the asthenosphere (Div2) to supply volcanoes located on either side of, but not at, the divergent boundary (Div3). All sketches reproduced with the written permission of the student authors.

TABLE I: Alternative conceptions (misconceptions) regarding plate tectonics.

TABLE II: Comparison of GCI scores for students whose sketches did or did not illustrate alternative conceptions (see Table 1 for alternative conception abbreviations).

TABLE III: Variation in GCI score and total number of plate-tectonics alternative conceptions compared to prerequisite-course experience.

TABLE IV: Percentage of student sketches illustrating alternative conceptions compared to prerequisite-course experience (see Table 1 for alternative conception abbreviations).

APPENDIX 1: Example of student worksheet.