Enhancing Quantitative Skills ofPhysical-Geology Students with a Geologic CompassGlenn Blair Stracher James Herbert SheaDepartment of Science & Mathematics Department of GeologyEast Georgia College University of Wisconsin – ParksideSwainsboro, Georgia 30401 Kenosha, Wisconsin 53141stracher@ega.peachnet.edu james.shea@uwp.edu

ABSTRACTAlthough the ability to use a geologic compass

is an important skill for geologists and can be auseful and stimulating skill for any student, mostintroductory geology courses do not include anywork on the use of the compass. This is unfortunatesince compass work, introduced early, can helpimprove the quantitative skills of all students bygiving them hands-on experience at solving prac-tical problems. The equipment needed is readilyavailable at relatively low cost and a variety ofcompass-based exercises can be designed tostrengthen student skills. Worthwhile exercisesinclude the following topics: quadrant and azi-muth notation, magnetic declination, compass-traverse closure, elevation measurement, distancebetween two landmarks, and strike and dip.

Keywords: Apparatus; education – geoscience; edu-cation – undergraduate; field trips, field study,summer courses; geology – teaching and curricu-lum; miscellaneous and mathematical geology.

INTRODUCTIONPhysical-geology textbooks and lab manuals gener-

ally fail to promote the geologic compass as an effectiveteaching tool. In the United States, geology studentstraditionally do not receive rigorous training in theuse of the compass until they enroll in a field-geologycourse, usually during the junior or senior year.

The geologic compass has been an indispensablefield-geology research tool for decades (Bartlett,2000; Reed, 2000), and teaching physical-geology stu-dents how to use one complements a course in whichboth geology majors and non-majors are enrolled. Ourjustification for teaching compass skills during twoconsecutive three-hour physical labs includes the en-thusiastic verbal response we have had from students.Most of them said they enjoyed the experience oflearning to use an instrument that many professionalgeologists use. Some students said the compass skillsthey learned were useful in locating themselves on amap while hiking. All students felt that learning touse a compass helped them understand angular meas-urements better than pictures in a book because itgave them something more concrete to work with.Other students in various disciplines are contemplat-ing undergraduate field-research projects requiringcompass skills. One such project, already underwayby a biology major, involves collecting water samplesfor analysis from wells and streams in Emanuel andJohnson Counties, Georgia. A compass is being used

in this project to determine the bearing and distancebetween collecting localities.

The authors believe that all educated individuals,regardless of their profession, should possess somequantitative skills in angular measurement. The geo-logic compass is an excellent tool for teaching theseskills to all physical-geology students, regardless oftheir mathematical background, while providing themwith the added benefits students themselves claimto receive. The purpose of this paper, then, is to pro-mote the geologic compass as a worthwhile comple-ment to physical-geology courses by emphasizing itsusefulness in building quantitative skills based onthe kinds of activities and calculations that manygeologists do while working in the field.

COMPASS SUPPLIES AND EXERCISESA variety of geologic compasses are available on

the market. Those offered by the Brunton, Silva, andSuunto companies are the most popular, with variousmodels in different price ranges. One particularlynice kit that is useful for classroom teaching is theBrunton compass and map-training kit illustrated inFigure 1.

Software and textbooks useful for teaching andlearning compass skills include those authored byHassinen (1998) and Compton (1985), respectively.

An instructor can design many different kinds ofcompass exercises. Topics we have covered includequadrant and azimuth notation, magnetic declination,compass-traverse closure, elevation measurements,calculating the distance between two landmarks, andmeasuring and plotting strike and dip. We use trigo-nometry in our compass-related exercises because itincreases the number and complexity of the quantita-tive exercises students can learn to do. Consequently,students are introduced to or given a review of thefundamentals of right-triangle trigonometry and thelaw of sines and cosines before being taught how touse the compass. The following exercises are exam-ples of compass-based exercises we find useful forenhancing student quantitative skills. Trexler (2000)and Dickinson and Hill (1997) have described addi-tional practical examples of the importance of com-pass skills.

Quadrant and Azimuth NotationThis simple exercise requires students to plot angles

on a sheet of paper and to convert between quadrantand azimuth notation, something many of our stu-dents don’t initially know how to do. Students arethen required to take compass bearings first betweendesignated landmarks on campus and then between

Journal of Geoscience Education, v. 48, 2000, p. 447

points on a topographic map. Theymust then convert between the twotypes of notation. After completionof this exercise, a written quiz isadministered to make sure studentshave mastered the necessary con-cepts. This exercise is easy for stu-dents to master, and many of themseem delighted that they are ableto use an instrument to make thekinds of measurements and angu-lar conversions that geologists do.In addition, this exercise is a goodlead-in to more complicated com-pass problems requiring calcula-tion of the distance between twolandmarks using the law of sinesor cosines as discussed later on.

Magnetic DeclinationAfter distinguishing between the

geographic and magnetic poles anddiscussing the significance of mag-netic declination, students are re-quired to interpolate declinationson an isogonic map by proportionand to contour interpolated decli-nations by hand. This exercise ex-poses students to another use ofproportions in geology besides mapscales and requires them to solvesimple equations for unknown decli-nations. Because of the calculations

required before contouring, this ex-ercise is more complicated then thesimple topographic map contouringthat physical-geology students doby connecting point elevations ona two-dimensional surface. It dem-onstrates to students the procedurea mapping geologist might have touse in order to determine the decli-nation to which his or her compassmust be set for accurate fieldwork.

Elevation MeasurementStudents are required to de-

termine the height of a building(Figure 2B) by using the tangentfunction. This skill may then beutilized in the field for calculatingthe height of a cliff if, for example,it is necessary to determine thethickness of an exposed outcrop ofhorizontal sedimentary strata. Theexercise requires students to meas-ure their distance from a buildingon campus and then the angle fromthe horizontal at eye level to thetop of the building. The tangentfunction is used to calculate H2, il-lustrated in Figure 2B, and thisdistance is added to H1, the stu-dent’s height, to determine the ac-tual elevation of the building (or acliff). Many students are surprisedthat it is possible to determine theheight of a building without hang-ing a rope off the side and meas-uring its length.

Distance BetweenTwo Landmarks

In this exercise, students use acompass to measure bearings be-tween landmarks on campus. Theyalso pace off the distance betweenthese landmarks on dry land. Afterdetermining the angles betweenbearing lines, they use the law ofsines or cosines to calculate thedistance between two landmarksseparated by a pond, as illustratedin Figures 2C and 2D. All our stu-dents immediately realize the use-fulness in applying mathematicalformulae to compass data acquiredin the field – the distance across apond can be determined withoutgetting your feet wet. The law ofsines is another example of usingproportions in geology, and the lawof cosines requires to students todetermine the square root of a num-ber after calculating with exponentsand the sine and cosine functions.

Strike and DipIn this exercise, students

measure the strike and dip of aninclined plane in the lab (Figure2E) and then on several beddingplanes in the field. We have foundthat the performance of studentson structural-geology exercises intheir physical-geology laboratorymanuals is enhanced after theylearn to measure strike and dip(Stracher and Shea, 1999). Studentsreport that they feel more comfort-able plotting strike and dip sym-bols in their laboratory manualsand that the significance of thesesymbols in revealing the presenceof folds on a map is more readilyunderstood.

CONCLUSIONSThe geologic compass is an ef-

fective tool for enhancing quanti-tative skills because it promoteslearning by doing. Developing andusing compass-based exercises is aninexpensive, convenient, and prac-tical way of enhancing quantita-tative skills including interpolationand trigonometry. Such exerciseshave the added benefit of providingstudents with an appreciation fora valuable research tool and theway it is used by many geologistswhile doing fieldwork. In addition,students are taught a skill usefulfor hiking and some undergraduateresearch projects and quite possiblyuseful later in their professionalcareers.

ACKNOWLEDGMENTSThe authors thank LeeAnn

Srogi of West Chester Universityand two anonymous reviewers forhelpful suggestions regarding themanuscript. In addition, we thankHeather Macdonald, of the Collegeof William and Mary, and LeeAnnSrogi for their efforts in organiz-ing and convening topical session60 at the 1999 GSA National Con-vention in Denver, Colorado.

REFERENCES CITEDBartlett, K., 2000, The more things

change…: Geotimes, v. 45, no. 3, p. 16.Compton, R.R., 1985, Geology in the field:

New York, New York, John Wiley andSons, 398 p.

Dickinson, W.W., and Hill, N.L., 1997, Anintroductory field exercise on topo-graphic mapping: Journal of Geosci-ence Education, v. 45, p. 221-224.

Journal of Geoscience Education, v. 48, 2000, p. 448

Figure 1. Brunton kit for classroominstruction includes 24 Brunton fieldcompasses, an instructor’s guide, in-struction booklets and worksheets,topographic maps and map symbolsheets, and a color VHS video withcompass lessons on topics rangingfrom magnetic declination to triangu-lation. The kit is reasonably priced atabout $325 US.

Enhancing Quantitative Skills of Physical-Geology Students with a Geologic Compass

Hassinen, A., 1998, Orienteering CD-ROM: 2151 Las PalmasDrive, Suite Carlsbad, California, Suunto USA, 92009.

Reed, T., 2000, The Brunton: Geotimes, v. 45, no. 3, p. 14-15.Stracher, G.B., and Shea, J.H., 1999, Enhancing quantitative and

map reading skills of introductory geoscience students with ageologic compass: Geological Society of America Abstractswith Programs, v. 31, no. 7, p. 209.

Trexler, J.H. Jr., 2000, Locating data on topographic maps, A fieldexercise in comparison of navigation methods: Journal of Geo-science Education, v. 48, p. 33-38.

Journal of Geoscience Education, v. 48, 2000, p. 449

Enhancing Quantitative Skills of Physical-Geology Students with a Geologic Compass

Figure 2. Compass exercises designed to enhance quan-titative skills, especially working with angles. Exercisesinclude: calculating closure for a compass traverse (A),measuring the height of a building (B), using the law ofsines (C) or cosines (D) to calculate the distance betweentwo landmarks, and using a compass with a clinometerto measure the strike and dip of an inclined plane (E).

ABOUT THE AUTHORSGlenn B. Stracher is Associate Professor of Geology

at East Georgia College in Swainsboro, Georgia. Hehas been active in undergraduate quantitative-skillseducation. During the past four years, he has taughtgeochemical thermodynamics at the graduate level inthe School of Earth and Atmospheric Sciences at theGeorgia Institute of Technology. Glenn is currently de-veloping a WebCT course in thermodynamics for GeorgiaTech He is co-author of a two-volume textbook in chemi-cal thermodynamics, recently translated into Japanese,and is currently co-authoring a new book in chemicalthermodynamics for engineers and earth scientists.

Jim Shea has been teaching geology for almost 40years and will be retiring from teaching in May of 2000.He has just begun his 26th year as Editor of the Journalof Geoscience Education. His major interest is in thehistorical development of geological theories.