College student conceptions of the scale of geologic time and the relationships between time and geological or biological events were evaluated through interviews, open-ended questionnaires, and student generated timelines collected from four institutions. Our data indicate students hold a number of alternative conceptions about the Earth's formation and the appearance of life, and these ideas are remarkably consistent across institutions. Transferability of these findings was evaluated via comparison with Geoscience Concept Inventory questions related to geologic time collected from 43 institutions nationwide. Detailed evaluation of student timelines reveals a notable disconnect between the relative relationships between the age of the Earth, the time required for the origin of the first life forms (prokaryotes), and the evolution of dinosaurs and humans. Students generally placed these events in the correct relative order, but had a poor understanding of the scale of time between events. Intriguingly, timelines can be mapped onto ternary diagrams, and the relationship between ternary diagram zoning and specific ideas of geologic time is explored. We found that some students, for example those with a young Earth perspective, map onto specific conceptual zones on ternary diagrams.
