Laboratory Exercise: What Controls Rheology?

Dyanna Czeck
University of Wisconsin- Milwaukee
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In order to understand the factors that control rock rheology, students conduct a series of activities with analogue materials. The activities are compared to real examples from the field and deformation experiments.

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undergraduate required structural geology course for majors

Skills and concepts that students must have mastered

Students must be familiar with the following terms and concepts: rheology, force, stress, strain, elastic, plastic, competence, deformation experiments, yield strength, ultimate strength, and rupture.

How the activity is situated in the course

This activity is one of many lab exercises students complete throughout the semester. It is followed by an in-class activity where the students use analogue materials to explore rheologic models such as Elastic, Newtonian, and Plastic.


Content/concepts goals for this activity

The students should gain an intuitive sense for the role of the following in determining the rheology of a deforming rock: lithology, stress, temperature, confining pressure, preexisting weakness, strain rate, and accumulated strain. They will also closely examine the important results of some deformation experiments and learn where natural deformation may help us learn more about rheology.

Higher order thinking skills goals for this activity

analysis of data, synthesis of ideas.

Other skills goals for this activity

critical reading of data presented in graph format, working in groups.

Description of the activity/assignment

A short laboratory exercise, conducted by students, is used to illustrate the multiple factors that contribute to rocks' varied responses to deformation. Analogue materials (play-doh, notebook springs, butter, silly putty, plastic bags, etc.) are used to illustrate many of the controlling factors such as lithology, stress, temperature, confining pressure, strain rate, preexisting weaknesses, and accumulated strain. The analogue experiments are presented in conjunction with parallel data from deformation experiments and field studies. The tandem presentation of analogue experiment and real data requires the students to obtain a natural "feel" for rheologic parameters and more exhaustively analyze the important conclusions obtained from field and deformation experiment data.

Determining whether students have met the goals

I help students with the exercises as needed. The students submit their written responses to the exercise for credit. The students use their understanding of rheology in future assignments.

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Teaching materials and tips

Other Materials

Supporting references/URLs

Davis, G. H., and Reynolds, S. J. 1996. Structural Geology of Rocks and Regions, 2nd edition. New York: John Wiley & Sons, p. 132-137.

Donath, F. A., 1970. Some information squeezed out of rock. American Scientist 58, 54-72.

Griggs, D. T., Turner, F. J., and Heard, H. C., 1960. Deformation of rocks at 500° to 800° C, in Griggs, D. T., and Handin, J. (eds.), Rock deformation: Geological Society of America Memoir 79, 39-104.

Heard, H. C., 1963. Effect of large changes in strain rate in the experimental deformation of Yule marble. Journal of Geology 71, 162-195.