ASSESSING STUDENT KNOWLEDGE OF EARTH’S PAST: A DEEPER LOOK AT STUDENT RESPONSES TO COMMON GEOLOGIC TIMELINE QUESTIONS

Time is inherent to geologic processes, however it is difficult to determine how students make sense of the vastness of geologic time conceptually, numerically, and scalably (Cheek 2012). The goal of this study was to assess student knowledge of the sequence and relative timing of key events in Earth’s history; describe and categorize how students represent geologic time numerically; and assess their understanding of visual proportional scales as represented by a simplified geologic timeline. A two-question assessment was adapted from Corrochano & Gómez-Gonçalves (2020) that included an existing, validated Geoscience Concept Inventory (GCI) question (Libarkin & Anderson, 2005) that asks students to identify the correct visual timeline for 5 key events in Earth’s history and a complementary question asking students to add numerical ages to the events on the GCI question. This assessment was embedded in an introductory-level geoscience lab course taken by majors and non-majors that covers a wide range of topics (e.g. earthquakes, rocks, waves, plankton, fossils) at a research intensive postsecondary institution in Canada. Student responses (n=87; 73% response rate) were assessed for correctness and were qualitatively coded using a priori frameworks established by the authors to describe how students represented numerical ages of the events. Most students (79%) could correctly select the timeline image with the correct order and scale of the changes in life on Earth over time. However, 36% students could not determine the correct age of any of the events and no students could correctly determine the individual ages of all of the events, suggesting further study is needed to determine how common geologic time data visualizations are interpreted by students. Almost half of the students (49%) used multiple number representation styles (e.g., 1.8 Ga, 1800 million years, 1,800,000,000 years) when labeling each event, suggesting students may conceptualize geologic time differently or inaccurately depending on how far back in deep geologic time the events occurred. This work has implications for practitioners seeking to assess students’ knowledge about Earth’s past. Pairing a visual geologic timeline assessment question with a numerical labeling assessment question may help instructors identify alternative conceptions students hold about key events.