Post-Instruction Alternative Conceptions about Plate Tectonics Held by Non-Science Majors

Plate tectonics is the conceptual model through which most dynamic processes on Earth are understood, and a solid understanding of the basic tenets of the model is crucial in developing future geoscientists and a scientifically literate public. The scale of plate tectonics in both time and space is inherently unobservable, necessitating the use of images and models communicating these earth-scale processes. We are interested in identifying alternative conceptions held by post-instruction novices related to plate tectonics and in analyzing the role ambiguous aspects in instructional images play in fostering alternative conceptions. To determine students' understanding of plate tectonics, we designed a questionnaire centered around a modified version of a cross-section supported by national geological organizations and widely reproduced in textbooks and online. Results from n = 495 non-geoscience majors enrolled in one of seven different introductory earth-science classes at a major research university or either of two community colleges suggest that many students retain or create a significant number of alternative conceptions regarding plate tectonics. We will report on a number of these alternative conceptions, including location of melting, sources of melt, and the relationship between topography and plate motion. For example, many students believe that the mantle is liquid, that the asthenosphere is a separate layer above the mantle, and that melting occurs both in the near surface trench and deep within the mantle. We also note that some figures commonly used to teach plate tectonics are problematic for students, and may actually result in reinforcement of non-scientific alternative conceptions. Further work directed at innovative approaches to teaching plate tectonic concepts is needed to address student conceptions, and to design images that do not detract from the central targeted theme. This research can inform curriculum development for entry-level geoscience courses.