This study published by the Journal of Geoscience Education addresses student conceptual understanding and conceptual changes in college science courses. Data were collected at a small private university, two large state schools, and one small public liberal arts college. Students were probed on a variety of topics related to the Earth's crust and interior, as well as geologic time. Analysis of questionnaire and interview responses indicates that students hold a number of non-scientific ideas about the Earth. Additionally, students apply a range of ontological categories to geologic phenomena, with significant implications for teaching geosciences from a systems perspective.