The initial knowledge of college-level introductory geoscience students is poorly understood, yet greatly affects the ability of instructors to create an effective learning environment. Here we review past research into several fundamental Geoscience concept areas to better understand misconceptions, alternative conceptions and preconceptions related to Geologic Time, Plate Tectonics and geohazards. We combine this review of past work with new research on what students understand about minerals in order to address the disconnect between instructors´ perceptions of their students´ initial knowledge, with what the students actually understand, in order to create a basis for decisions on course structure and pedagogy.