PROGRESSIVE ALIGNMENT OF GEOLOGIC TIME

Students in the geosciences struggle to understand geologic time. Difficulty arises in part from the discrepancy between how people perceive and remember events in time and science’s conception of time as a single metric dimension. People tend to think in terms of familiar event units that range in magnitude bounded by a human lifetime. The current study examines the role of magnitude in understanding geologic time and reasoning about events that extend beyond the range of familiar experience. An intervention was designed based on the common classroom exercise of aligning time to a spatial representation. The intervention was designed to give students practice aligning time to space. Using progressive alignment, students aligned time to space beginning with a familiar personal time scale, working through different historic and geologic timelines, up to the Geologic Time Scale. Half of an undergraduate introductory-level geology class participated in the intervention activity after a stratigraphy lab, and the other half completed only the stratigraphy lab. All students completed outcome measures one month later after finishing two fossil labs, which explicitly taught concepts relevant to geologic time. The intervention group showed a reduction in the magnitude of temporal location errors compared to the control group on an item from the Geoscience Concept Inventory on geologic time. Intervention students were less likely to indicate that the dinosaurs appeared more than 230 MYA. The intervention group was also more accurate on a multiple-choice item that required students to identify the correct duration-based statement using a conventional diagram of the Geologic Time Scale. This item is a new measure of geologic time developed for use with middle school students. On both measures, the intervention group demonstrated a more accurate sense of the relative proportions of geological events. Importantly, the intervention and control groups did not differ significantly on an item that was knowledge-based and did not require an understanding of magnitude. This suggests the intervention affected understanding magnitude of geologic time, and did not merely increase effort or motivation in the intervention group. How this intervention fits into a broader program of understanding geologic time will be discussed.