HOW DO THEY KNOW WHERE TO GO? EXPERT VERSUS NOVICE REASONING AND NAVIGATION DURING BEDROCK GEOLOGIC MAPPING

Bedrock geologic mapping is a complex and cognitively demanding form of problem-solving. The geologist must navigate through an often unfamiliar area, identify and interpret scattered outcrops, and construct a 3D mental model of the rock structure underneath. Decisions about movement though the field area and reasoning about what is seen are deeply intertwined; moment by moment the geologist decides where to go in order to collect data or test a working hypothesis, then uses their observations to decide what to see and where to go next. Work over the past decade has shed light on how students and experts approach mapping, but much remains unknown.

This study examines the interplay between navigation and reasoning by examining the GPS tracks and verbal data of 67 novice (undergraduate student) to expert (professional) geologists who mapped a ~1 km area in the Rocky Mountains, Montana, USA. The GPS tracks of six experts were used to identify 25 m, 50 m, and 100 m cells that five of six experts visited. All 61 non-expert tracks were then compared to these cells. For all non-experts, the more cells visited at all scales, the more accurate was the distribution of rock types on the participant map. However, visiting more of the 25 m cells correlated with a more accurate understanding of the underlying geologic structure (a syncline and reverse fault) for non-experts. Post-mapping interviews reveal potential explanations for why time in expert locations yields a better structural interpretation. First, experts report forming a structural interpretation immediately to very early in the task. They talk about navigating through the field area with reference to the geologic structure and key locations (e.g. the nose of the fold, the fault trace). Individuals who produce accurate structural interpretations share these characteristics. In contrast, those with less accurate maps, often novices, discuss their navigation strategies as wanting to cover the area and see as much as possible. Findings have implications for how we teach students to make deliberate navigation choices as they are learning the art of geologic mapping.