THE 4th DIMENSION: TEACHING THE CONCEPT OF TIME USING GOOGLE EARTH

Understanding time is critical for geologists, yet for students this is one of the most difficult and challenging concepts to grasp. Although the emphasis is generally placed on deep time, the understanding of geologic processes occurring over shorter time scales (<10³ years) is especially important in subdisciplines such as geomorphology. Understanding the rates of natural geologic processes is important for evaluating the impact of humans on Earth’s systems and critical for land-use planning and sustainable decision-making. Topographic maps are the traditional approach for teaching geomorphic processes, landforms, and dynamics. The static nature of topographic maps makes it challenging for students to understand and appreciate the dynamics and magnitude of processes that do not occur at constant rates over time. Only in rare cases does a series of topographic map editions for the same area for three or more different dates exist. Introduced in Google Earth version 5.0 (released in 2009), historical imagery allows users to access and analyze imagery dating back to the 1940s in some locations. This imagery is useful for studying geomorphic processes including fluvial dynamics and landform evolution, coastal erosion, sand dune migration, landslides, glacier retreat, and the influences of climate change. In addition Google Earth provides measurement and elevation profile tools, allowing users to make quantitative assessments and interpretations. Several examples using Google Earth to teach geomorphic change over time in coastal environments will be presented. Student performance on Google Earth (82.5%) activities was significantly higher than traditional topographic map (76.8%) activities. In a feedback survey, 100% of students reported that Google Earth enhanced their understanding of geomorphic change over time.