TEACHING GEOLOGIC MAP INTERPRETATION USING GOOGLE EARTH

The interactive 3D terrain viewing capability of Google Earth makes it a terrific resource for teaching geologic map interpretation. Using tilt, rotate, and zoom, students can see the third dimension directly. Google Earth satellite images in many places show strong, contrasting colors for bedrock units. The Google Earth 3D view helps students visualize that the color bands are actually layers that extend below ground. This is an enormous break-through over previous approaches that we’ve used, where many students see map units as 2D paint stripes.

In our approach, students do their own geologic mapping in Google Earth before they know anything about strike, dip, or types of contacts. Being able to tilt and view from any direction allows students to make their own geologic maps successfully, despite having little or no experience. They can also see directly which way contacts are inclined. The tilt and fly-through views also help students successfully sketch topographic profiles and cross sections. The emphasis of this approach is on visualization, rather than on memorization of patterns and rules. Areas that lend themselves well to this are listed at http://serc.carleton.edu/NAGTWorkshops/structure/google_earth_mapping_locations.html

While many instructors start with horizontal contacts because they seem simpler and don’t require defining strike and dip, we start with inclined contacts because they are actually easier for students to “see” in Google Earth. Once students have made maps and cross sections of inclined contacts, we use the Google Earth 3D view to develop an understanding of dip. We then use Google Earth to derive strike after students understand dip. Students then make a geologic map and cross section of a monoclinal structure (such as the Raplee Anticline) and work out how the outcrop pattern of eroded horizontal contacts differs from that of inclined contacts. Students work with vertical contacts last, and the Google Earth 3D view is again instrumental in helping students visualize erosion of vertical contacts. After creating several more maps and cross sections of areas viewed in Google Earth, students generalize the concept of outcrop patterns and begin to work with “flat” geologic maps. This approach is described in detail at http://serc.carleton.edu/NAGTWorkshops/structure/approach.html