GeoScape: An instructional rock garden for inquiry-based cooperative learning exercises in introductory geology courses

Journal of Geoscience Education, Mar 2003 by Calderone, Gary J, Thompson, J Robert, Johnson, Wayne M, Kadel, Steve D, Et al

The students were provided with an air photo of the area (similar to Figure 1) and standard mapping tools including tracing paper, colored pencils, a compass with clinometer, a tape measure and a couple of tent stakes. The exercises include: construction of a topographic map, construction of a geologic map, interpretation of the geologic map and the history it represents (cross section, map key and written report), and solution of practical problems related to resources (coal, metal, groundwater, etc.) exploration. Following the lead of Peter Kresan (1995) at the University of Arizona, who designed a set of laboratory exercises to discover the Lost Continent, these exercises are prefaced or introduced with the idea that the students are now the geologists in a remote, geologically unmapped territory and it is they who must apply what they have learned to serve their society. While many of these exercises are directed to help students build science skills specific to geologic investigations, students also experience inquiry and problem solving by analyzing data and manipulating mental models to unravel the geologic history ofthe area (see Alcock, 1994, and Siebert and McIntosh, 2001 for other examples and background). The field mapping requires the student to synthesize new information from the observations and from their knowledge of earth materials and processes.

Construction of a Topographic Map - The goal for this exercise was for students to construct a topographic map on a piece of tracing paper overlain on the aerial photograph. This map was to contain information similar to that shown on a standard United States Geological Survey (USGS) map. We decided to begin with the most basic of data, the determination of geographic North and magnetic declination. Students were instructed to determine True North using the motion of a shadow produced by a vertical stake (the change of the position of the shadow's tip after 15 to 20 minutes is approximately a west-east line). Once True North was established, students compared this direction to the direction shown by the compass needle to determine magnetic declination. Students quickly learned that magnetic measurements are adversely affected by the proximity of strongly magnetic objects like the metal stakes they used for their solar determinations. Although this method ot determining True North often had errors approaching 10 (depending on the patience and care of the students), every group was able to show that that the magnetic declination was not zero and was to the east of true north as is the case in Glendale, Arizona. Many groups actually estimated the magnetic declination within 50 of its actual value. These data were placed in the appropriate location on their new topographic map. While waiting for the shadows cast by the vertical stakes to move, students determined a scale for their map by measuring a feature common to both the aerial photo and the actual ground. The area is barely large enough for accurate determination of latitude and longitude using new hand-held GPS receivers (10 meter resolution). Consequently, we are able to have students determine latitudes and longitudes for each corner of the map and show them the utility of GPS. For topography, we told the students that surveyors visited the area beforehand and placed different colored stakes marking elevations (bench marks) in the relatively flat area of the map. The colors of the stakes indicate specific elevations. In the future we will probably install more realistic benchmarks into the landscape or have the students actually determine elevations with a transit and trigonometry. Neither the butte nor the mesa, however, was staked although one stake was placed at the base of the butte. The students were instructed to use their tape measures to measure the heights of the features, determine a contour interval appropriate to the data and draw the contours on their map. Finally, the students added standard USGS colors for vegetation, water, etc., and had fun creating fictitious names for the surrounding quadrangles.