Visual Metaphors for Teaching 3D Geological Thinking and Interpretation
George H. Davis
Department of Geosciences, The University of Arizona, Tucson, AZ, USA
Promoting understanding through visual metaphor is commonplace in the teaching of structural geology, especially when we try to convey the 3D structural geometry and deformation mechanisms. When I began writing the very first (1984) edition of Structural Geology of Rocks and Regions, I found that I just had to embed cartoons and non-geologic imagery in ways that reflected the explanatory language, sketches, and photographs that I employed in teaching undergraduate majors. As a teacher I always like to ease into a topic, moving from the familiar to the less familiar to the unfamiliar. Visual metaphors (now numbering 55) therefore became a staple in the 2nd (1996) and 3rd (2012) editions of the textbook. I use them to pave the way for comprehending the meaning and significance of terms, concepts, and processes. Moreover, I use them to model how structural geologists think about systems of structures within Earth's crust. David F. Fischer is the artist who transformed my designs, sketches, and word pictures into cartoons in all three editions.
Metaphors most typically present themselves as analogies within one of the four main rhetorical modes of written and spoken discourse: exposition, argumentation, description, and narration. Effective metaphors are used sparingly and selectively, and practitioners generally make efforts not to mix them. Language framed in metaphors permits 'seeing' knowledge in a new perspective. Visual metaphors especially permit the viewer to grasp how visual space is organized and provide a means of conveying how things are to be 'seen' and understood (St. Clair, 2000). Ideally, visual metaphors are conveyed in ways easily interpreted, usually because they evoke everyday objects and familiar experiences. Optimally, pictorial representations are delivered with just the right level of detail, neither too simple nor complex (Williams). In order to 'work', visual metaphors should be chosen with due attention to cultural and generational context (Gombrich, 1963).
Visual metaphors convey understanding through experiencing one kind of thing in terms of another. Within any effective metaphor, it is obvious that the two things being compared are dissimilar in every way, except for the context in which the metaphor is being framed. Through visual metaphors, unfamiliar territory becomes understood in terms of familiar territory. After all, the root meaning of "metaphor" is a "crossing over" (Jerry Hogle, University of Arizona, personal communication, February 2013). What I hope 'crosses over' for students is rapid grasp of meaning impossible in any other way.
What interests me most is whether student exposure to a steady diet of visual metaphor enhances the transition from propositional thinking to visual understanding. I have not tested this, nor would I know how to do so. But cognitive scientist Mary Peterson (University of Arizona, personal communication, February, 2013) believes that pictorial representation becomes enhanced through "grounding in experience", which can include, in its many forms, the grounding achieved through effective visual metaphors. As one of her teaching strategies for effective reading of journal articles and textbooks, Dr. Peterson urges students to turn immediately to a visual figure when it is first cited. Timely examination of the figure thus provides grounding in experience that enhances understanding during the next step: reading and studying that portion of text for which the figure was designed. Peterson (personal communication, February, 2013) pointed out that psychologist Larry Barsalou at Emery University has a body of research indicating that human understanding of abstract concepts is grounded in perceptual experience.
In preparation for this conference, I have reviewed each of my visual metaphors in Structural Geology of Rocks and Regions, and ended up classifying them into 3 types.
Some are static, focusing on pairings of geometric form:
chevron folds/paper airplane
conical fold/ice cream cone
point defects/parking lot
pi-diagram/timbered mine tunnel
angular shear/Saskatchewan barn
Some are less static, with implied motion:
thrust duplexes/pick-up cabs on flatcars
joint patterns/craquelure in master paintings
flexural-slip fold/paperback book
blind thrust/telephone book
deformation paths/bowling trajectory
deformation/hot air balloons
diffusion creep/the 15-14-13 game
Still others, the ones I consider to be the most productive for teaching, are explicitly kinematic in nature, capturing the movements that lead to final geological forms.
detailed structural analysis/pepperoni pizza
salt dome kinematics/handkerchief
propagation of disclocations/ballroom rug
pore-fluid pressure/beer can experiment
transform faulting/Los Angeles freeways
stress concentration/ice skating
salt welds/patio furniture
deformation/flocks of birds
The conclusion that I reached in this 'inventory' becomes a premise to be tested at the conference, namely: that visual metaphors most successful in conveying kinematic processes are likewise the most effective in grounding the 3D visualization of final forms and shapes. When kinematics of creation of final 3D forms are grasped, it becomes easier to visualize the complete 3D forms, even when only small bits of the final forms can be observed in the field or in the subsurface.
St. Clair, R. N., 2000, Visual metaphor, cultural knowledge, and the new rhetoric, in Reyhner, J., Martin, J., Lockard, L., and Gilbert, W. S. (eds), Learn in Beauty: Indigenous education for a new century: Northern Arizona University, Flagstaff, AZ, pp. 85-101.
Gombrich, E. H., 1963, Meditations on a hobby horse and other essays on the theory of art: Phaidon, London, UK.
Willliams, V. S., Creating effective visual metaphors. http://www.personal.psu.edu/staff/v/q/vqw/Portfolio/VislMeta.pdf
AAPG Search and Discovery Article #120140©2014 AAPG Hedberg Conference 3D Structural Geologic Interpretation: Earth, Mind and Machine, June 23-27, 2013, Reno, Nevada