Think-Aloud Modeling of Geologic Reasoning in the Field

Stephen J Reynolds, School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287
Arizona State University at the Tempe Campus, School of Earth and Space Exploration
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Initial Publication Date: May 21, 2012 | Reviewed: July 6, 2017


In a field class, the instructor shares all thoughts with students as the group examines outcrops, roadcuts, or geologic traverses. Such thoughts include observations, possible interpretations, what additional information is needed, potential strategies for approaching problems that arise, doubts about what is knowable and what is not, and anything else that comes to the instructors mind.

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Learning Goals

Geologic field studies require incredibly diverse types of thinking, involving geologic background information, 3D visualization, possible strategies for approaching the problem, logistics, and many other aspects. A field geology course or experience should impart to the student the various ways of thinking that should occur during the fieldwork.

Methods of Geoscience

This activity helps develop geologic reasoning skills by helping students to the following:
(1) distinguish observations from interpretations,
(2) make predictions and brainstorm what data are needed to evaluate a prediction,
(3) consider different strategies for approaching a field area, and
(4) appreciate the impact of incomplete data.

Context for Use

This activity is appropriate in any field class, including an introductory field class, Structural Geology, Field Camp, or an Advanced Field class. I have done this approach at all of these levels to great success. It can be done in the context of a normal field trip stop or at the start of a several-day field project.

Description and Teaching Materials

This activity involves explicitly sharing with students all the thoughts that occur to the instructor, as they occur, in the field. The approach is to take students to a field area, outcrop, or roadcut with as little as possible front-loading of information, such as readings from a field guide or lecture upon arriving at the field site. Instead, the students are invited to observe the field site and discuss with classmates their observations, possible interpretations, any questions they have, etc. After a sufficient amount of time, the instructor gathers the class and walks through the field site and shares ALL thoughts that arise. This is not limited to the typical way an instructor tells students "this is that and here's how it formed", but instead is a sharing of all thoughts, including:
(1) kinds of background knowledge that are being accessed, even at the most basic level (e.g., hornblende is more common in andesite than basalt);
(2) what key aspects are being focused on and which ones are being downplayed (e.g., this is layering but that is rock varnish);
(3) specific criteria that are being used (e.g., is this metamorphic rock homogeneous or heterogeneous);
(4) strategies that are being employed or at least considered (e.g., I should proceed from the least deformed part of the outcrop to the most deformed part);
(5) possible interpretations, even those that are quickly discarded (most instructors do not share these with students);
(6) ideas about aspects of the geologic history that arise from the observations and interpretations, including how these fit or do not fit into the regional setting; and
(7) any tangential thoughts to which the outcrop leads.
In other words, the instructor is explicitly modeling the entire thought process for the students, not a pre-edited, tidy version. If we want students to think like a field geologist, we should show them exactly what we mean, dead-ends and all.

Teaching Notes and Tips

This sharing of thoughts takes more time than your average "look, talk, and go" field-trip stop, so plan on at least twice the amount of time you might normally take at the field stop. But if higher-order thinking is one of your main goals in a geology degree, its time well spent.


This activity is rather hard to assess. One indication is anecdotal, consisting of what students say about the approach and how they perform on other field stops. A more direct way to assess the activity is to have students construct a concept sketch about the field stop. This would consist of a simplified sketch that, in this case, should be annotated with observations, interpretations, predictions, additional information that is required, nagging doubts, and any other aspect that is appropriate for that particular field site. It could involve multiple sketches that show not only the evolution of the area, but what types of data support each step in the reconstruction.

References and Resources

If an instructor is going to use concept sketches for assessment, they should examine the following articles:

Johnson, J.K., and Reynolds, S.J., 2005, Concept sketches – Using student- and instructor-generated annotated sketches for learning, teaching, and assessment in geology courses: Journal of Geoscience Education, v. 53, p. 85-95.

Tewksbury, B.J., Reynolds, S.J., and Johnson, J.K., 2004, Using student-generated concept sketches for learning, teaching, and assessment in structural geology courses, Geological Society of America Abstracts with Programs, v. 36, no. 5, p. 347. (see also various documents on the SERC website)

Lucas J. Reusser, Lee B. Corbett, and Paul R. Bierman, 2012, Incorporating Concept Sketching Into Teaching Undergraduate Geomorphology. Journal of Geoscience Education: February 2012, Vol. 60, No. 1, pp. 3-9.