Introducing Field-Based Geologic Research Using Soil Geomorphology Martha Cary Eppes1 ABSTRACT A field-based study of soils and the factors that influence their development is a strong, broad introduction to geologic concepts and research. A course blueprint is detailed where students design and complete a semester-long field-based soil geomorphology project. Students are first taught basic soil concepts and to describe soil, sediment and rock properties using standard description procedures. Then, with minimal geological or field experience, they are led to design and execute a project that examines how soil properties differ as a function of processes, parent material and time. By designing and executing the semester-long project, students gain familiarity with the entire geologic research process including basic field observation, hypothesis development and testing, interpretation and presentation skills. During the course, students learn 1) the basic knowledge necessary to describe geologic materials (soil, rock, sediment) in the field, 2) to make observations and interpret them in the context of geologic hypotheses which they have developed, 3) to develop, and execute a field-based research project, 4) to integrate and draw conclusions about complicated semi-quantitative data sets, 5) to map and survey in the field and 6) to present their research in a public forum. By the end of the semester students are able to make and test hypotheses relating soil properties to the depositional environment, age and/or type of geologic deposits in which they form. The knowledge, skills and research experience gained in this simple, semester-long project serve students well in upper-level courses and beyond. An example project is presented from a 2nd order stream and its adjacent tributary alluvial fans in the Piedmont of North Carolina. INTRODUCTION beyond introductory geology. Numerous similar For a geologist or soil scientist, a soil is a soil geomorphology studies exist for the western naturally occurring body of roughly horizontal United States (e.g. Gile et al., 1981, Busacca, 1987; layers (horizons) located at the surface of the earth McFadden et al., 1989; Reheis et al., 1992; whose morphological, chemical, biological and Bockheim et al., 1996); however, very few have morphological properties are altered from that of been undertaken in the temperate climates of the the original sediment or rock from which they eastern seaboard, and fewer still in the Southeast have formed (parent material) (e.g. Buol et al., (Levine and Ciolkosz, 1983, Markewich and 1997). Soils defined this way are distinct from Pavich, 1991; Lichter, 1998). Thus, the project those defined by an engineer who considers any allows students to collect original data that can unconsolidated natural material a ‘soil’. A contribute to the field of study. geologist’s ‘soil’ is essentially the weathering rind This type of inquiry based learning is a of the Earth’s surface. Thus soil properties are recognized and recommended pedagogy (Barstow directly related to- and provide insights into- the and Geary, 2002) that many find difficult to processes and characteristics of the atmosphere, incorporate into lower level undergraduate course biosphere, hydrosphere and lithosphere. work (Apedoe et al., 2006). Nevertheless, Over the past four years, a central component numerous workers have demonstrated that such a of the lower level undergraduate soil science teaching approach will improve students’ overall course at the University of North Carolina at science-related skills and understanding, Charlotte (UNC Charlotte) is the development of including critical thinking and hypothesis a soil geomorphology study that examines how development and testing (e.g. National Research soil properties vary in a landscape as a function of Council, 2000; Keller et. al., 2000; Cavello et al., the characteristics of local environmental 2004; Garvey, 2002; Gomezdelcampo, 2006). conditions. For the majority of students, this Furthermore, numerous studies have clearly course is one of the first that they have taken demonstrated the benefits of field-based learning in introductory level geoscience courses (e.g. 1University of North Carolina at Charlotte, Department of Geography and Earth Sciences, 9201 University City Blvd., Elkins and Elkins, 2007; Fuller et al., 2003; Bogner, Charlotte, NC 28223; [email protected] 1998). Commonly cited difficulties related to such Eppes - Introducing Field-Based Geologic Research Using Soil Geomorphology 11 Figure 1. Soil Description Sheet modified from Birkeland (1999) with permission from David Harbor (previously David Jorgensen). Used in conjunction with ‘cookbook’ instructions for describing soils (Birkeland 1999, Appendix 1), this sheet includes basic components of a complete field description of a single soil pit in a temperate climate and is consistent with description procedures outlined in Soil Survey Staff (1993). field-based courses include expense, travel time throughout the semester in separate lectures; and student-teacher ratios (e.g. Williams and however, a separate lecture is not necessary for Griffiths, 1999). Because soils (weathering the field-based component of the course that is profiles) are ubiquitous, however, lack of bedrock described herein. Soil textbooks such as Birkeland outcrop does not preclude completing a soil-based (1999), Buol et al., (1997), Schaetzl (2005) and study, which can be developed on even the most Brady and Weil (1999) are all good references for urban of college campuses. Furthermore, basic the following basic soil-geomorphology concepts soil field data (e.g. Birkeland, 1999; Soil Survey that should provide a sound starting point for Staff, 1993; Appendix 1) are similar to those of instruction. geomorphology and sedimentology, so most A soil profile is described in a similar manner geologists have the background knowledge to a rock outcrop. Birkeland (1999; Appendix 1) required to develop such a course. Also, the provides a manual for how to dig a soil pit and repetitive nature of soil descriptions allows for describe a soil profile that should be read and working with 3-4 students at a time in a 20-30 reviewed by the instructor and employed by student class, while other groups are engaged in students while in the field. This appendix is a activities that they are comfortable with. Finally, manageable summary of a significant body of the skills and concepts learned during such field- widely available soil description literature. In based coursework have been demonstrated to be particular Soil Survey Staff, 1993; and portable to other courses and to be professionally Schoeneberger et al., 2002 are both available for enriching (Kirchner, 1994). Here I describe a free on the web and are excellent resources for the blueprint for the UNC Charlotte course that could instructor if necessary. be employed by almost any geoscience Description of a soil profile incorporates a department as a 2nd tier introductory level field- description of secondary weathering features based course. related to soil development (e.g. horizons, colors, soil structure) as well as any primary features SOIL GEOMORPHOLOGY CONCEPTS inherent to the parent material such as At UNC Charlotte, concepts of pedogenesis sedimentary stratigraphy, grain size, or and soil geomorphology are taught to students mineralogy. Beginning at the ground surface, soil 12 Journal of Geoscience Education, v. 57, n. 1, January, 2009, p. 11-22 Figure 2. A. Location map of study area in North Carolina. B. Topographic and geomorphologic map (typical of those produced by students for the exercise) of Toby Creek field area. The topog- raphic map is provided to students for an ‘office mapping’ exercise. Contour Interval is 2 feet. horizons are typically vertically stratified with 1941). All five factors influence the suite of notable horizontal boundaries. Horizon chemical and physical weathering processes that boundaries mark changes in weathering serve to create any observed soil profile. Soils characteristics and are located by marking forming on toe slopes (an aspect of the ‘relief’ significant changes in observable properties such factor), for example, will often exhibit as color, structure (natural particle arrangement), redoximorphic features such as mottled coloring texture (grain size), induration, root content and/ as a result of developing in a wetter soil climate or visible pores. Horizon boundaries may or may than their backslope counterparts. Differences in not coincide with stratigraphic boundaries that microclimate might then be attributable to mark different sedimentary or rock units. Once differences in the runoff and runon of these two horizons are determined, a standard suite of soil landscape positions. properties is described for each horizon in a If four of the five soil forming factors are held profile (Figure 1). Horizons are named according constant for a group of soils, then the influence of to an accepted nomenclature, A, B, C etc., the remaining factor on soil development can be depending on their properties. In a very general determined. A soil chronosequence, for example, sense, A horizons are zones of leaching and of is a series of soils whose properties vary primarily additions from the ground surface (e.g. dust in as a function of the age of the exposure of the arid settings, organic material in humid settings). surface on which they are forming. Deposits or B horizons are zones of accumulation and in situ surfaces of similar age should share