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How Old is The Earth? An Exploration of Geologic Time


"Geologic time is fundamental to the study of the Earth and life sciences, but it is an abstract and difficult concept for students to master. We predict that placebased inquiry, in which students directly engage with authentic and meaningful local landscapes while interpreting physical evidence for geologic time, will be at least as effective as more orthodox expository methods in imparting geoscience content knowledge, such as the concept of geologic time. This outcome, coupled with the enhanced relevance and interest inherent in the method, would favor its use in naturally and culturally diverse settings such as the Southwest United States. As a preliminary test of the effectiveness of place-based inquiry, we designed and administered two 2-part inquiry lessons on relative and absolute geologic time, based on Arizona landscapes and rocks, to 52 in-service middleand high-school math and science teachers enrolled in an experimental graduate course in biology, geology, and mathematics. The teachers' knowledge of geologic time before and after the lessons was assessed using the Geoscience Concept Inventory, a valid and reliable survey. We analyzed pre-test and posttest means with a non-directional dependent samples t-test and reject the null hypothesis of no mean differences, t(49) = 5.35, p < .01. We conclude that there is a significant gain in the teachers' content knowledge related to geologic time before the inquiry lessons (Mean = 11.66, SD = 2.93) and after the inquiry lessons (Mean = 9.74, SD = 3.57). The teachers who participated in the class reported that the place-based lessons were particularly engaging and ranked them among their favorites for the experimental course. Place-based teaching methods in geoscience merit further study at the undergraduate and graduate level."