BREAKING STUDENTS’ MENTAL MODELS OF ROCKS BY BENDING THEM

Elastic Rebound theory and seismic wave propagation are both common topics in introductory geology and geophysics courses. Enabling students to fully conceptualize these concepts can be challenging since students’ everyday experience with rocks does not normally allow them to experience rocks’ elastic property. To enable students to develop mental models of these concepts, physical models such as the Earthquake Machine, the Booby Trap model of intraplate earthquakes, and Slinkys have been developed and employed in geoscience classrooms. Here, common elastic materials such as springs and rubber bands allow these models to function like their targets (e.g. lithospheric rocks). Despite their functional similarities, there is evidence that following the use of these models, students are able to convey the basics of the intended concepts, but still do not fully accept that rocks are elastic. To address this shortcoming, a classroom demonstration of rocks’ elastic properties was developed. To test the efficacy of this demonstration, a quasi-experimental study was conducted in both a 100 level introductory geoscience lab setting where sections were assigned to one of two treatments, or to a control. In the control, a traditional example (e.g. a rubber band analogy) is used. In treatment 1, the demonstration is used. In treatment 2, the demonstration is incorporated into a hands-on lab. To document students’ prior conceptions of rocks, and assess the impact of the treatments, pre- and post-assessments were employed to measure concept learning (e.g. rocks are elastic), as well as students’ ability to apply this concept to novel situations that haven't been introduced yet (e.g. other solids can also be elastic, explaining a diagram of the elastic rebound theory). Initial results indicate that following the demonstration, significantly more students were able to accurately describe how to demonstrate an object’s elasticity to another person, recognize rocks as being elastic solids, and extend this understanding to other common rigid solids. It also appears that despite recognizing rocks as elastic solids after the demonstration, students have difficulty scaling this new understanding of rocks as elastic solids up to include the notion that large slabs of the lithosphere (e.g. plates) also behave elastically.