USING SOILS TO TEACH GEOLOGIC MAPPING: AN INTRODUCTORY-LEVEL IN-CLASS EXERCISE

Most introductory geology students think soil is just the dirt they walk on and do not appreciate how it influences their lives. We have created an in-class inquiry-based exercise that involves making a simple soils map of the region where our students live. This exercise has been done with classes ranging from 25 to 75 introductory-level geology students. Initially, we ask that each student bring a soil sample from his or her home or other location. They must take care in sampling to avoid contamination and human influences (e.g., mulch in a flower bed). This could be expanded to include a soil profile for a lab-class. Next the students classify their soil on a ternary diagram based on simple grain size estimation. This is an intellectual challenge for many introductory students who are taking geoscience, as they perceive they are weak in mathematical and graphical skills. Once they have classified their soils, they use a shared computer to input their location data and soil classification to create a GoogleEarth KML file. This information is then shared with the entire class and contoured to create a soils map representing the samples they have classified. To conclude, we compare their findings with a published soils map and typically find that their product reproduces this fairly well given their sparse, incomplete data. We then discuss how the soil influences other factors in their lives such as housing construction, local flooding, crop production, etc. After this exercise, they appreciate that dirt is more than something that needs to be washed away.

Students are also engaged in data collection and the process of doing science to supplement their text. This exercise can be applied to future classes as they can relate their knowledge of soils to other geologic processes. This simple, yet open-ended, project allows freshmen to begin to develop research skills applicable to further science classes of any type. In addition, they are involved in doing group work. This exercise builds fundamental scientific research skills and provides practice in other basic skills our students need (algebra, writing, map reading, public speaking).