This manuscript has been submitted to the Journal of Geoscience Education, published by Taylor & Francis. It has not been reviewed or accepted.
A revised version of this manuscript has been published in the Journal of Geoscience Education (online publication date 17 Jan 2019). The accepted version is available online at https://www.tandfonline.com/doi/full/10.1080/10899995.2018.1548004 . The accepted version will be posted here after the open access embargo period (18 months) has passed.