Novice earth science students often have difficulty visualizing three-dimensional interpretations of flat, two-dimensional displays. This challenge becomes apparent when students attempt to comprehend topogaphic maps. In this study, we investigated conditions that influence such activity. Earth science students viewed standard topographic maps, maps that included shading, maps that included stereo visualization (affording a three-dimensional percept of the map), or maps with both stereo visualization and shading. Students answered line-of-sight questions (i.e., intervisibility tasks) while viewing their assigned map. These questions required students to visualize a route-perspective from the map's survey-perspective, with particular attention to the terrain relief. Tasks like this are routinely completed during topographic map experiences, and provide insight into a user's understanding of the dynamic land surfaces conveyed by those maps. Overall, stereo visualization was more successful than shading in facilitating students' completion of the task. Students' general performance was not influenced by gender, but was influenced by other background characteristics (e.g., expected course grades, prior map experience, and predilections for outdoors activity). Students also preferred maps employing three-dimensional cues more than maps without them. Classroom activities in the earth sciences may benefit from incorporating stereo visualizations into map-learning exercises.