Nationwide pre- and posttesting of introductory courses with the Geoscience Concept Inventory (GCI) shows little gain for many of its questions. Analysis of more than 3,500 tests shows that 22 of the 73 GCI questions had gains of <0.03, and nearly half of these focused on basic physics and chemistry. We also discovered through an assessment of nearly 500 matched pre and posttests that students were less likely to change answers on basic physics and chemistry questions than they were on those for the geosciences, with many of the low-gain geoscience questions showing switch rates that were similar to that expected for guessing. These results also pertain to the high-scoring pretest students, suggesting that little geoscience conceptual entrenchment occurs for many students enrolled in entry-level courses. Switching rates for physics and chemistry questions were well below the rates associated with geosciences questions, suggesting greater entrenchment. We suggest that students may have difficulty settling on a correct geoscience conception because of the shaky, more entrenched supporting science underpinnings upon which Earth Science ideas are built. These results prompt the following questions: (1) When do our geology majors learn fundamental science concepts if little learning occurs in the introductory courses? (2) What role does the introductory course play in this eventual learning? (3) What strategies can be employed in introductory courses to enhance learning for those students who will only take one college-level geosciences course? We suggest that longitudinal studies of geosciences majors are needed for periods longer than a semester and that more attention be paid to when conceptual change occurs for our majors.