HOW STUDENTS COUNT TECTONIC PLATES IN VARIOUS CROSS-SECTIONS

Although plate tectonics is a fundamental concept in geology, we do not have a good understanding of the difficulties students have with basic concepts, such as the ability to count the number of tectonic plates in a schematic depiction. In this study, after learning about plate tectonics in an introductory geoscience course, 784 students from 17 classes across the United States were directed to count the number of tectonic plates in 16 different cross-sections illustrating a variety of combinations of plate boundaries, oceans, and continents (some cross sections were combined with views of the surface). Six cross sections were designed so the same situation (e.g. a continent next to an ocean with a divergent boundary) was shown using a simple black-and-white line drawing as well as using a detailed color cross-section combined with a surface view (3 paired questions).

In agreement with previous work (Kortz et al., 2010), preliminary analyses indicate that students had difficulty counting the number of tectonic plates in all cross sections. Overall, students responded with the correct number of plates 58% of the time, although the range of responses for individual cross-sections varied from 29% to 74% correct. By class, correct responses by students ranged from 32% to 79% correct for all cross-sections. 11% of students correctly counted the number of tectonic plates in all cross sections. Interestingly, some questions were answered differently by students of different gender and ethnicity. For most students who answered some questions incorrectly, our initial analysis did not find a consistent line of reasoning they followed to count the plates on the different cross sections. In response to the 6 paired questions, students gave the same response to both questions on average 62% of the time. Students were more likely to answer the simple line drawing depiction correctly (63%) compared to the detailed colored depiction (53%). Our preliminary results indicate that, even after learning plate tectonics, students do not have a good grasp of some of the fundamental concepts.